When you really get stuck, I find there's only three real options:

1) Call it quits. This is best when you realize that the reason your stuck is because you don't mesh as partners, but not my preference. Sometimes, this just has to be done because the arch and climax of the story you are telling has completed. Movies and books end too. This might be why I'm rarely a fan of an "extended universe" for movies I enjoy as stand alone stories. It's supposed to be begining, middle and END.

2) Walk away temporarily. Maybe even by moving with the same partner to another story line for a while that contrasts the current one. Absence makes the heart grow fonder and all that, but so can shaking things up a little. If the current story I'm stuck with is strictly modern/realistic, I will try something heavy on fantasy in a totally different setting for a while. Eventually, I can return to it with a fresh outlook.

3) Introduce something crazy to inject some unexpected action into the story. For example, if I've got a character just sitting around on a date, feeling bored and forcing small talk - why not have an NPC character rush and hold up the diner? An earthquake could strike! Aliens could land. Hell, there's a host of possible ways to throw a bit of chaos into the mix. To me, this is the most fun option by a long shot.