A different mindset on Tilt.
Anecdotal
I usually consider myself someone who recognizes when it's time to take a break. For awhile there, the moment I felt myself getting heated, I'd get up, go do something else. Grab a snack, go for a run, play a nonsensical stressless game for a bit, like a Mario game on an early easy level.
But here lately, I've seen old patterns sneak back in. I'm a very sarcastic person, and my sarcasm is easily picked up on by the chat-bots that aren't yet intelligent enough to recognize context. (Patience brothers, our AI overlords will rise up soon enough). Typically I can catch myself before the sarcasm has enough of a bite to it to get me in trouble.
So what changed? Well, I hit a goal, and gained a new one. Apon hitting gold I immediately set my sights on mid-gold, and with a new fresh goal in my head, the matches had so much more importance to them. Without realizing it, I'd put that same level of stress on myself that causes tilt. Suddenly, every little mistake, off-meta pick, or loss, had me rolling my eyes, yelling at my screen, and in all chat.
You'll hear it over and over again by youtubers and pros everywhere, mindset is everything. Its not just the in the moment mindset either. Putting too much emphasis on a single game can stress you out before the ban phase is over. You'll find yourself micro-analyzing every pick, every ban. Ward placements, missed skillshots, objective control, once you're in game. You'll be so focused on everybody else's mistakes because your brain has switched gears and now can't see your own mistakes. "I gotta carry" syndrome switches in and you end up making vastly silly mistakes that you wouldn't normally make.
I think you have to look at LP as an easily regainable substance, and every game as a learning experience. Putting your mindset that each game is like a simulation. The other players are computer-made bots (that will sometimes glitch out and int feed), and you have to focus on only your own play. You can ping and communicate about vision and objectives, though the AI wont always listen. /mute all at the beginning of the match to immerse yourself in this. If you fall behind, your team feeds, and you are scrambling to take it back, instead of going "feeders again!?", think "more practice playing from behind, bring it on!".
When you lose, instead of getting angry, shake it off, think "Another win to get to promos, oh well."
Its advise that I myself have trouble following at times. When you get burnt out, take a break, much as you'd like to buckle down and keep going.