It's something you have to force yourself into. I was watching some old poker after dark clips of Ivey playing full ring. I noticed that even when his decision was obvious, he always stopped and gave a 5 count before making a decision. Had me rethinking a lot of different advice I've heard. In no particular order:
-Go into your hands with a plan. Don't just put chips in the middle hoping to hit. Think through what you'll be doing in the face of Cbets, wet flops, etc.
-Use your time. Force yourself to take 5 seconds to rethink what you're doing in the hand and how it fits with your overall strategy.
-Constantly be evaluating your play and adjusting to the table, but don't change your overall strategy mid-session. If you think you may need to make adjustments to your opening ranges for different table compositions, rework your three bet range and sizing, etc, spend the time after the session to evaluate. Strategy changes made mid session are going to be weighted by bad beats and emotion. Spend time away from the table thinking strategy and make your larger decisions there.
-As soon as you realize you've made a tilted decision, leave the session. Doesn't matter if you're down. Chasing losses while tilted is a sure way to make them deeper.
Those are the ones I've come to take as gospel, and every one of them will help maintain discipline.