Do the same thing every time. Don't worry about "focusing", just do the same thing every time and you will automatically focus and make less mistakes over time. Have a very good pre-shot routine, stance, stroke - all fundamentals rock solid. It'll make much less difference in how you play when you're tired, nervous, etc and you'll dog less shots. Self-talk is important too, read some books on mental game for different sports (not just pool). It's a journey and will take time, after years of playing I've only really started working hard on this recently and it's an eye opener to say the least.
awesome..thanks for your help...
I have read a few books on the mental side of things..
A mind for pool
Pleasures of small motions..
In the Zone(not a pool book)
The inner game of tennis
Golf is not a game of perfect
Talent is overrated
Any other ones you can think of that i should check out??