I will give my answers - just like a confession statement of a  **Doubting Thomas**  (DT)  type trader .  It is in deed an exercise - introspection. 
When he missed a lot of good chances to make handsome profits....
His conscious was querying him. 
 and he was trying to find an answer
He said:  “My biggest Mistakes  when trading ...
Lack of Consistency - Inconsistent - my inability to be constantly Consistent... Nothing else...”
 
Q:  Why inconsistent...??   
DT:  Fear of loosing money...
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Q:  Why are you afraid of losing money...???  Don't you have a clear cut trading strategy ...
DT:  Yes, I do have a nice trading system -  In fact it was thoroughly  back tested  for  4 - 5 years  and  forward tested  more than a year.... but  then...
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Q:  but then.... what?
DT:  See... I have a clear cut  entry / exit strategy -  I knew what I have to do... but  I was hit with some whiplashes.... I was terrified... I closed my trade positions.... the moment I closed and sat idle  the market  started trending  from the predetermined trade-able level .... by the time I realize it... it was too late...
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Q:  Why did you sit idle...?  Have you not realized from your back tests & forward tests that,  there are always chances of some whipsaws...??
DT:  Yes,  I know... that was there..  while I designed my trading system / strategy.. I know it is not a holy grail...  but it is an effort to find an edge over others... it is a proactive effort to minimize  whiplashes.. 
At the time of back testing every thing looks fine - the results were encouraging - the handsome profits on the results eclipsed the small losses on whipsaws...  
When I forward tested with paper trades...  No hard cash was involved... there too  handsome profits points were glaring so brightly,  these whipsaw losses were shadowed.
The problem of inconsistency sprouts,  only at the time of real trades...  When I loose money with small whipsaw losses continuously on three or Four trades.. I am sacred...  Once I am away,  market starts trending...  I missed the bus.
And one more major  pit fall is  changing  the position size… frequently --- that affects  the overall performance
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Q:   Is there any thing else  that scares you... other than whipsaws....and makes you inconsistent ??
DT:  Yes….Gap up and Gap down openings.....  and  major event like Brexit
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Q:  Can you elaborate...??
DT:  Assuming I don't have any position....  market open with a nice gap....
But gap up/down opening price point is some where far-away from the predetermined entry / exit trigger price level....What should I do...?  
The long or short entry price point must be nearer to the predetermined level only,  so as to minimize the loss in case market reverses.... I wait for it happen 
At many times,  I found  market runs up or down - continue to move on the same direction as per gap opening - without even a small pull  back.. I missed the bus...  How do I say it...??  Is it inconsistency...? 
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Q:  And what about major event  like Brexit...??
DT:  That is a wonderful case study... I love to share here...  
On the date of referendum  Nifty run up and up... As per My system / strategy  - Long position was triggered...  
In normal circumstances.. I would have bought deep in the money call options and kept it open...  Since the next day referendum results will be out...  I closed all my long trades  and  kept nothing in the position.
Next day market tanked... I was happy  and thanked God for giving  sanity on right time.... Every thing looked nice..  I shorted Nifty as per my level....  that shorts were stopped out with some small profits  and  simultaneously  long positional call was triggered....
There my inconsistency virus hit me badly...  I was not convinced about the long trigger... because every one on TV were crying bear.... waited / waited and waited for the market to come down once again... It never happened... Market was moving up and up  in front of me  and my heart was burning...
There are two things here I noticed.... Two questions that are haunting me...
Am I  right  in NOT taking long trigger  on the day of referendum  and kept my positional longs over night....???
Why I did not go long - when my triggers say so - on the day results were out....???
If these are all  NOT inconsistency --- then what they are...??  
Look at the intraday chart of Nifty - June'16 contract  to see my trade triggers... to witness what I missed...

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Q:  I can understand your feeling....  But do you have solution...??   How are going to come out of this simple but gigantic problem...???
DT:  The root cause of inconsistency is Fear.... 
So, only solution is - Kill the fear....to ahcieve  Fearlessness - निर्भयता
This is will come  only if I have a sound risk management - - It should be versatile – 
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Q:   How....??
DT:    After  great difficulty – achieved  self- discipline  as to NOT to change  the position size…. And this is one of main / prime catalyst that gave a decisive first blow to the fear.
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Q:  After that…?
DT:   Did some serious home work – took refuge in mathematics.  In fact,  it is an interesting thing when I was working to find out a guidance as to whether the price action reached  over bought  or  over sold levels….  I got a nice by-product  which highlights certain price action area that is prone to whipsaws.   
So, when my pre-determined entry / exit levels  comes with in the range of whipsaw area… I donot trade on those levels.
See the attached chart:


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Q:  And then…?
DT:   One more area that is prone to whipsaws  were also identified…. That is LTPR… Last Traded Price Range…  I apply some percentage point up and below  the LTP (previous contract expiry date)  - If any of my trade trigger levels comes within that range… I avoid that level for that contract… Example -  for trading July’16 contract – I check up the LTP of July’16 contract as on 30-June-2016.
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Q:  Fine….  Then what about  other fear factors  like  gap up / down opening  and ensuing major events….??
DT:  To kill the fear in such scenarios…. I decided to hedge my positions…  I prefer  Vertical spreads  and some time  Diagonal spreads…  I know clearly that,  this hedging exercise would not nullify the risk in toto… but considerably reduce the impact of pain,  if price action reversed / goes against my position…. Also remember such hedging will cost you some  profits  if the price action goes as per the direction expected.
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To sum up -  It is inconsistency  that poses direct threat to any trader…  he might be having a world class trade setup / system…. But it is uselss – unless make use of it consistently every time – all time. No compromise on it.  
Also  he must be serious enough  to NOT to change the position size as per his own discretion.   Position size is to be determined well in advance as per his own risk taking capacity that varies person to person.   Serious study should have to be done before determining as to how much quantity to trade – All pros and cons should be studied , analyzed & understood in detail. Once it is determined it cannot be changed…
And the best part is:  understanding these weaknesses / impediments are essential…. That will decide how far a trader will be successful – who sleeps peacefully during night… and enjoy weekends with his family regularly.
Wish you all happy and safe trading..