 Maybe learning a new language or an instrument or even a relationship. Philip says to stop and consider why you're trying to keep at it. Does this thing or this person make you feel more alive or more frustrated, more upset or angry? If it's the former, keep at it. Tough things are worth the challenge. But if it's the latter, it might be time to let that thing go. And think of it like this. You'll have more time and energy for something else.