No matter how much physical training you do, if you stall out on moves (be it during an onsight or redpoint) and fail to commit, then application of this physical training fails at the first hurdle. Some ways we can try to combat this: 

1- Working moves on a difficult section of a route or boulder: If you are going to give a sequence a go, once that is the plan commit to it fully. Don’t get halfway through and wonder whether or not you should try something else. By doing this you will more quickly get a better idea of what is and what isn’t working, and save time and energy in the long run. 

2- Away from working moves, and when climbing in an onsight or flash fashion the same ideas can be applied. Force yourself to commit and be happy with failure if it doesn’t work out. Long term this will produce a more confident climber, and in the short term you may be rewarded for this commitment by fluking your wat through incorrect sequences and still hanging on, or by climbing the correct sequence really efficiently. 

3- If typically you are a confident climber and have found yourself lacking commitment of late, it may well be that you are feeling the effects of Mental Fatigue. Check out Coach Cams Training Tips piece from the from the 26th January for more details on Mental Fatigue.