The rules for the mutually miserable

1. If your girlfriend wants to see other people, ask out her best girlfriend and see what happens. In the worst case, you could end up dating two high maintenance women, and in the best case, you could be free.
2. Bring cards, flowers & say "I love you" at least as often as you make love. Consider this preventive maintenance, and keep in mind that women are more fragile than your pickup truck, and need maintenance more frequently than every 3000 miles.
3. If she expects you to call her, tell her a time you'll call, and call her at that time. Otherwise she'll either sit by the phone waiting and whenever you call will be "too late" and she'll have given up and gone out, in which case remember rule #1.
4. Don't put up with bullshit. Once you start, you'll be neck deep in it. Then again, there is actually probably no way known to man that you can be in a relationship and not end up putting up with some amount of bullshit. Establish appropriate bullshit management techniques. Take care in attempting to use reason and logic, as these operate in different ways for different genders. Also take care in attempting to use anti-reason and anti-logic, as these generally fail to produce consistent, repeatable results which establish trust and respect. Whatever approach you take, use it consistently at all times, unless inconsistency is called for (see rule #3).
5. Pride, Respect and Trust are cornerstones of your being, and her's too. Don't violate them, or allow them to be violated. If you do, you are done for, even if the appearance of passionate love remains. Love is not strong enough to overcome lack of pride, lack of respect or lack of trust; these are the foundations on which stable love rests.
6. You've got to stand for something or you'll fall for anything.