I used to get upset every time I tried a new task. A stroke makes me slow and clumsy when I try something new. My performance goes downhill as I get more and more frustrated. I finally learned to think of my first attempt as a rehearsal rather than practice. Coaches will tell you to work out with the team, but that does not mean they will let you play in the game. Music teachers want their students to practice, but they do not expect most of us to do anything with the instrument we are learning to play. In therapy, practice takes the form of exercises and Activities of Daily Living (ADLs) without knowing how these activities will change my life.
Rehearsal, on the other hand, implies a later performance in the real world. For example, if I have trouble zipping my coat I stop and rehearse pinching my hemiplegic thumb and index finger together before I grasp the zipper pull. If I know an item will be difficult to find in a store, I rehearse saying the item's name before I go in the store and ask an employee where the item is located.
Thinking of my first attempt as a rehearsal changes how I feel. I try to remind myself that even professional musicians don't expect to be perfect the first time they play a new piece of music. If my frustration escalates to anger during my first rehearsal I stop the task. When I try the new task the next day I am quicker and more coordinated. Sometimes the mistakes I made the day before give me an idea for how to make the task easier. Able-bodied people are amazed by how well I do things. I do not tell them I rehearse.