It’s like that fuse on the Mission Impossible intro. Something bad happens and the fuse is lit. You work it out and pinch the fuse and the fire goes out. 
Something else bad happens and because you didn’t replace the fuse with forgiveness last time you don’t get to start the discussion of its resolution at the beginning. You relight the fuse, the frustration, the fight, right there at the place you left off last time.
The situation goes nuclear and in the rubble of the blast you wonder how it got this bad this fast this time.
Forgive. Replace your fuses. Give each other some more slack. Really start over. It’ll require a choice and some follow through. It’ll be worth it.