Slow down a moment before acting. Take a breath and think about what you're doing and why you're doing it.
If I'm betting, am I betting for value or for bluffing? Or for pot control? Do I want my opponent to fold or to call?
If I'm folding, why am I folding?
If I'm checking, why am I checking instead of betting? Or instead of folding ? Am I hoping to check raise? Is my opponent LAGgy enough to bet out when I check in front?
If I'm calling, why am I calling and not betting? Am I open limping?
If I bet OTF, then what will I do OTT?
It really doesn't take but half a second to pause and think about what you're doing and why you're doing it, before acting. It made a huge improvement in my play when I stopped my snap decisions.