I'm in love with you, but I still have feelings for that person who is also in love with me! Who do I pick? Usually the unemployed dumbass because he's the bad boy who is trying to reform.
I liked that on Grimm, when there was a triangle going, they didn't really go back and forth... They dealt with the relationships like grownups and while there may have been some residual feelings it didn't stop them from moving forward. As Eve said, "No regrets."