Yeah you're in much, much higher elo than me but I think I can still help you out :)

So, to be less toxic, I think you need to control yourself in game. Try to look at the positives in each game. For example, if your teammates get first blood, commend them! If your teammate is feeding, verbally abusing him or her will not help. Instead, try to encourage them to play safe and tell them the game isn't over yet. You might genuinely be losing or the game is pretty much lost but if you're positive to your teammates and positive in your thinking, you might not feel so bad.

Now I have read that you take League into the physical world. League is competitive and like any sport whether it is an eSport or not, people will feel upset and frustrated, just like you. When this happens, calm down! Watch a movie or a funny show. Comedy will cheer you up and you're bound to feel better. A very important part of this all is that League is just a game. That is how it is. Raging over a game isn't worth it and you need to repeatedly tell yourself this.

If you're on tilt, just don't play the game. It sounds like League is something you play a lot and it's fine but when you're not playing well, just stop! If you don't actually want to do anything else, just play normals with the intent to have fun. You don't need to win normals, they're not on your record!

So just to conclude, play every game like you want to have fun and always be positive, whether you're winning or not. Remember if you're not having fun or are on tilt, just go do something and else and trust me, you'll feel better.

I used to rage too. I went from my placement at B2 down to B5. However, through reforming my way of thinking, I've made it back to B2 and I am very determined to make it to Silver.

Good luck friend and never give up!