Sometimes you get stuck, and it looks like there's no way forward.

Thomas Edison found himself in this situation many times:

"When you've exhausted all the possibilities, remember this: you haven't."

When you're stuck you can start by affirming your confidence that there is a way forward.

You can list your assumptions, in the most neutral way possible, and then challenge them one by one.

You can take a break and do something completely different, preferably physical activity. You may get a great insight when you come back.

You can look at all the successes you've had so far and think how they came about. These patterns may give you insights on how to tackle this problem.

You can talk to others about what you're struggling with. Explaining a problem in its simplest form often yields new insights.

If you don't have someone to talk to or you don't want to bother them, you can explain the problem in writing, as simple and eloquent as possible.

You can set a time limit and when it passes, set a time when you'll revisit the problem.