Try to imagine the worst thing that could happen. Usually, it’s not catastrophic enough to warrant the anxiety you feel about it.
Figure out all the levers you can pull on to make things go your way. When there’s uncertainty, that means there are big factors you can’t control, but there are usually still some factors you can control.
For going through a hard time:
Think about another hard time you’ve gone through that seems like it’s now in the very distant past. Someday, this thing will feel that distant too.