There is always room for improvement. My father used to always tell me that the day you were satisfied with your performance was the day you needed to quit because you would no longer have the drive to improve.
At the end of practices I often have players ask themselves if they played as hard as they could have at practice. The answer can never be "yes". You can always go harder. You can always do one more sprint. You can always cheer on your teammate a bit more. There is always something you can be working on. There is always more to be done. That is why it is called practice. When you practice something like yoga, medicine or the law you are always improving and never reaching ANY final destination.
ATHLETES ARE ALWAYS IN PRACTICE!!!
You can always improve as long as you never lose sight of the purpose of athletics, which is to consistantly challenge yourself in hopes to improve.