How to stop think what if?

... not overthinking and able to make decision wisely?
Plus, is it irrational to think what if not works?
The reason I thinking the worst scenario is I want to rebound from it and have guidance in case that happen (which nobody wants but shits happen).

Thank you. Because I really need it right now.
Arrgh. My stupid incompetent brain please work with me.
😖😭