Finish fast, finish strong!
Hey tzvarnoharno,
Many are in the same position as yourself dont fee alone
The following article should provide you with all the tools to continue your journey improving on your chess: How do I get better at chess?
Regards
Richard
The answer is puzzles, puzzles, puzzles. The more you practice tactics, the more likely you'll notice them when they pop up in a game.
Also, don't relax your concentration when you have a winning position. The better your position looks, the more likely it is that there is a nice tactical shot that can just end the game.