A great step forward is taking on a defense mindset (and mind you, some never do). You can win much more by thinking about defense before shooting!
Take a few moments before any shot to consider all three options of offense, defense or both in a single stroke, and raise your winning percentage at least 50%, perhaps more. What do I mean by three options rather than two for offense and defense?
1. The option to "go for it" on offense to try to win the game, sinking the balls remaining for victory. This is often how to shoot pool--if you're an amateur!
2. The option of defense, which could leave the opponent a possible lock safe, from which they have no possible reply on offense.
3. The option to play both at once, a fine two-way shot, composed of offense with defensive possibility or vice versa. In other words, thinking about where the balls likely go following a miss and choosing a shot that is a win if you make it, safe if you don't.
One good example will show you the way. Learn how to shoot pool better, with just one sample shot concept.