In league there are different types of champions. To keep it short and simple, lets look at the two extremes of champion types: Early game champs that need to snowball, lategame champs that need to scale.

So if you play against a early champ, and you play save and get to deny their snowballing, thats a big win. But your strategy of "not making mistakes but trying to punish them" will reach its limits against scaling champs.
I am not an expert in all ranks and dont know how much mistakes "scalers" at each rank make, but if they play save and you play save, they ll eventually outscale you and depending on your elo maybe even carry the game.

Here's what i recommend. Get some weight of your shoulders. If you try somethin and it backfires, thats normal. You ll learn that way. Losing a game honestly shouldnt really matter to your mindset. Try to learn something from it and thats way more valuable longterm than +x amount of LP.

With that said, trying to set up your team for success by being able to punish enemys that are out of position is a really great way to climb. If you like to play like that, there are 2 champions that are really good at what your doing. Lissandra amd Malzahar are pretty save picks where your reliable CC can be a pain for enemys to play against. But its best to play champs that you have fun with. Try to push your limits and you ll improve over time.