i dont know your age... but have you ever played poker?
there is a lot of psychological things a poker player does to not tilt with the swings of a hand, a game, or tournament. alot of is leaving your emotion behind and playing with calculated logical decisions. when you play on emotions you tend to act rash and dont make great judgement.
that can translate to league... dont play if you are upset, tired, mad, depressed whatever if you want to avoid tilt. and if you are playing leave that when you hit QUEUE for a game. its gone. and from there everything you do in game should be made with a calm ,logical , calculated mindset.
things arent gonna go your way all the time. its how you react when they do...
and another thing with poker is what they call poker face/ stone face dont let your inner highs and lows show on your face. well with league in your game/play or chat to the enemy. dont give any tells, dont give anything away...
alot of things in league are determined by level, experience, items, #s advantage in a fight... cooldowns, and positioning in lane and in fights. similar to poker things are determined by table appearance, are you a tight player , loose, aggressive, passive. what position you are in the hand... chip count/size , pot size, pot odds. are you vs 1 as in heads up or multiple players in a hand. do you have a tell on a player like you picked up how they play with a strong hand in early position , how do they play if they are weak. what tells have you given indirectly (not knowing) or on purpose to make someone call/fold react a certain way due to your actions at that moment.
so as you can see the mindsets can easily transfer from one game to another... its learning this and knowing the psychology behind it that will benefit you alot from not tilting.