First: Have other options, and don't cut yourself off from them. That means always keep more than one plate spinning, and never promise commitment of any sort. I'll explain later why this is important.

Every time your partner shows undesirable behavior:

Decide if the offense is a dealbreaker.
If it is, take a step back from the relationship ("Soft Next" her).
If it isn't, relax and don't let it bother you.

Why does it work?
Relationship problems are generally caused by broken rules and over-familiarity.

By "rules" I refer to unspoken beliefs that usually involve the word "should" or "must".
"She should have called me back." "She shouldn't have acted like that." "She has to see that I'm right about this." And so on.

Over-familiarity occurs when two people spend too much time together and share the same space for too long. Subconsciously, you and/or your partner start to feel that you don't have to put as much time and effort into the relationship as you did at the beginning of the relationship. It generally takes months to years for this to occur.

"Rules":
The more rules you have, the more likely it is that one of them will get broken, and that generally causes drama. Eliminate as many shoulds and musts from your life as you can. I recommend Albert Ellis' books for this.
The few rules that remain should be important enough to end a relationship over.
If it's not important enough to end the relationship over, it's not worth getting frustrated by.
In any questionable situation, ask yourself "Am I being treated well?" If the answer is ever "no", you need to immediately take a step back from the relationship.

Soft Next:
Don't explain anything, just break off all contact with your partner for a minimum of a week. Spend this time working on your own goals, socializing with friends, and sleeping with other women.

Warnings:
Dropping off the grid is a dick move if you have a girlfriend or wife. Becoming a boyfriend or husband essentially tells her "I'm not going to end the relationship without communicating," and following these rules would essentially break that promise. This is why you shouldn't promise any commitment. Perhaps not surprisingly, this is also why women push for monogamy: to keep you from disappearing and to reliably keep you in their lives.

Of course, as stated earlier, the longer they reliably have you the less effort they put out to keep you. This is a Bad Thing.