It's just Baseball. As others have said, failure is part of it. Just in the last few weeks I've seen my kid take better at bats than he ever has in his life and take at bats that his 11 year old self might have had a better approach with.
The key, as a player, is not to ride an emotional roller coaster on every up & down moment. Stay focused in the right now. Trust your preparation, and if necessary do a better job with your preparation. Baseball is a game of an adjustments.
For hitters, sometimes it is a matter of approach: hunting fastballs, being aggressive, getting ahead in the count if they are pitching around you,or jumping on that first fastball if they are coming right at you.
For pitchers, sometimes it is a matter of changing your pitch sequence, disrupting the hitter's timing, pitching to a hitter's weakness, and learning how to set up your out pitch.
It is a wonderful game. But, maddening. Which makes it all that much more wonderful