character was always fucking up

That reminded me. In BitD a lot rides on presentation. Try to not make failed/complicated rolls about the characters failing but the circumstances not being in their favor, instead

They didn't break the lockpick - they noticed a nasty trap in the lock just in time to not get stung, the lock will need more work
They didn't get hit when grappling with a guard - they hear footsteps approaching (trauma in general is the least interesting choice, unless you feel it's time for it to appear in the story) They didn't make noise when sneaking by - there was a loose plank in the floor they had no way of noticing

From my experience, when you most often aim at coming up with new external problems (like those footsteps), characters will start to bounce off them, instead of just progressing through the story. It might feel like you can't ever really challenge them but on the other side of the table something can always come up and they have to constantly think on their feet, which simulates the feel of a heist.

Unless placed so it builds tension, "you missed" most often just breaks the flow of the plot. It's a temporary setback that doesn't build anything. "You got him clean but it's the funny/irritating/popular/w/e guy among the guards. Everyone knows him. I'm marking first piece on alarm clock because sooner or later they will notice he's not around tonight" - that builds tension and the world even if during this heist it will be the last piece marked on that clock