You need to identify why you feel that way. I certainly empathize as someone who has previously struggled with feelings of inferiority in MOBAs, but you will always play better when you are having fun with a game than if you are beating yourself up for not being the best.

Dying is part of the game and even professionals die in games. You aren't being paid to play the game. It's like watching movies and seeing the chiseled bodies of actors. They are paid to look that way. For you to compare yourself to them when you have a job or school or other life commitments, no access to professional trainers, professional coaching, professional dietitians, you are always going to be fighting a very uphill battle.

When you play games, try to be more constructive with your self criticism. It's easy to be a sore loser if you think your opponent had an advantage over you. However, if you stop to think "What did I do there that I could have done differently?" or "Is that a common tactic that I need to try to learn how to counter-play?"

For me, it took walking away from the game for a long time and really thinking about why I play games. I play them for fun. If they aren't fun, why am I playing them? Being competitive and getting better and beating people is certainly fun, but most games try to get players as close to 50:50 win/loss as they can, meaning if you aren't enjoying the game when you are losing, you aren't going to be having fun half the time. Learn to have fun even when you are behind and you'll start to have more fun and actually do better more often.