Record your games using replay.gg or something similar. Watch your games, multiple times if you have to, and learn from your mistakes. Understand how bad your decision making is, how dumb face-checking that bush was and question yourself at to why you tower dove like an idiot for something that was absolutely not worth it.
You can literally become better by simply asking yourself questions as to why you do things the way you do and what you could or should have done in those situations.
For example, a jungler could ask himself those questions:
- Why are you taking mid farm when your mid laner is coming back to lane and the wave isn't gonna crash into tower?
- Why are you invading the enemy bot side jungle when both your bot and mid lane are being pushed to their tower?
- Why are you not at Dragon when your bot lane killed their bot lane, mid is pushed to their tower and their jungler is top side?
The answer to those questions are simple:
- Get the hell out of mid lane, you are stealing from your mid gold and effectively slowing him down against his own lane.
- Get the hell out of their jungle and go gank. If you get found in their jungle, you'll have their mid and bot lane rushing to you for a free kill because they have complete control over the bottom half of the map and your own mid and bot won't be able to help you.
- Get your ass to Dragon RIGHT NOW.