Map,
I am certainly not a great player (unless of course you are judging by enthusiasm only

); but most of my competitive pool has been 14.1, and I have played with and taken lessons from some of the best - so I'll pass along some things that have helped me immensely in competition (as competition is COMPLETELY different than running balls in practice).
The Number One Rule is MAKE THE BALL YOU ARE SHOOTING. Do not let thoughts of position or match outcome IN ANY WAY distract you from the job of pocketing the ball at hand. You will lose many more games by missing a ball than you will by missing position. Be RELENTLESS in your adherence to your pre-shot routine and mechanics on EVERY shot, no matter how easy it may appear. Every shot should be taken the same way, whether it is early or late in the match. Do this, and you are already ahead of most of your opponents.
Avoid any and all low percentage shots (play safe instead). Avoid any and all sequences that involve 2 or 3 "80 percent shots" in a row. Avoid ANY thoughts of high runs. If you think a break shot is too tough, then just play safe (or pot it and then play safe if it's too tough to get into the rack). Learn and position yourself for the side of the rack safety that gives you an 80% chance of winning the resulting safety battle. Avoid the top of the rack and bottom of the rack safeties that give you only a 50% chance of winning the resulting battle.
Do NOT get discouraged if you hit a rough patch. Almost all mortal players will lose their stroke for a few innings here and there. If you handle it with equanimity you are a step ahead of an opponent who doesn't. Don't get discouraged in any way if your opponent is cleaning up an easy rack - it's a long game and you will have your chance.
When its late in a long close game; rely completely on your mechanics with NO thoughts of outcome or penalties for missing. Choose ONLY sequences that end with you running out the game with all easy shots or end with you playing a planned safety; at this stage of the game, pressure is very high and you want only easy shots. Oh yes, and I might have mentioned before, have fun (you are playing the game of champions), stay always cheerful (this disturbs some opponents, but you don't really care) and POCKET THAT FREAKING BALL.
P.S. - if SJM disagrees with any of this, listen to him instead.