After years & thousands of dollars in trading, the single greatest thing I did to save money and create more was to stop trading by 12pm EST.
I'm up and trading at 8am EST (bonds/currencies), indexes (930am) and continue trading till 12pm EST.
I view 1 trading day as 3 completely different and unique cycles:
Cycle 1 (AM session): typically plenty of movements taking place, whether from econ news, orders set to go on the open, etc.
Cycle 2 (Lunch): volume can dry up and so can the movements.
Cycle 3 (PM session): 50/50 on whether you will see volume, which usually equates to movements.
It comes down to how you trade and what you are looking for. Personally, I need things to be moving in order to make money. I know that usually these moves will occur during the AM session almost every single day.
I also know that from 12pm - close, it's a 50/50 shot on whether you will see volume come in, which could provide movements.
In the end it's all about your trading style though. I know some guys that can kill it during what I call 'chop' and that'd get killed during what I call 'movements'.