Steven Pressfield tells us about a little trick screenwriters use to start developing a story. They start at the finish. They work out the climax first and then work backwards from there.
You can develop the same habit when you practice. First you figure out where you want to be, then you work backwards.

How can you do it?

Most times it’s easy because the Finish is given to you by external circumstances. It’s either a gig, audition, rehearsal, or music lesson.
Put the date of the gig into your calendar, then work backwards and determine what you have to practice to get there. To get there and play your best performance.