I can do all things through him who strengthens me. This verse is often used as a motivational quote. But Paul wrote it from prison. It is not about self-optimization, it is about contentment in every situation.
Paul had learned to be full and hungry, to experience abundance and lack. His strength did not come from circumstances but from Christ. That is rest, not because everything is going well, but because the source is firm.
You do not have to accomplish everything today. You may live from the strength of the one who works in you. This is not a pass for passivity but an invitation to act from trust, not panic.