Relationship? To me it's like food. Good food go well together, they compliment one another and though they don't always look okay when put next to each other, they're still great!
Whatever it is (how bad your relationships may seem) only you can tell if it'll go north or south. Some food class like to go through the ileum, others prefer to end up going through the lacteal and others... well, let's just say they go north or south (depending on which way is up..)
While everyone has their own views on this matter (take out food from the context please~) I trust the best answer goes to religion. The Book has taught us guidelines in maintaining a healthy relationship + a bonus on healthy gastronomical system! (*does the term even exist? :p).
Whatever you choose, choose carefully. Coke doesn't go great with mentos and you won't do so great with someone too. Remember that, live your life as it is, make the necessary changes if needed & move on when all else fails! God-willing, someone better is waiting for you at the end of the line :D
Pray hard, be strong, be happy and S-M-I-L-E =)