Question

Worrying does not empty tomorrow of its troubles. It empties today of its strength.

Answer 1

Shortened: worrying is temporary and you should stop and smell the roses some times not worrying about everything

Answer 2

It means just because you're worried about something - and obsessing about it to the point where you can barely focus or do much - it won't change tomorrow's outcome. Whether the outcome's good or bad. It's just telling you that you should basically relax because at the end of the day, whatever's going to happen is going to happen. Worrying today only messes up your today.
I hope all is well, and I helped! (: Good luck, rockstar! If you need any help, or have any follow up questions or comments, let me know! (: