Riot used to do infinitely stacking chat restrictions, as in you'd never escalate to a ban (except in extreme cases) for chat offenses and would just keep getting restrictions. However, this policy was not conducive to reforming the player, as they'd keep abusing their limited chat and stack up hundreds or thousands of chat restrictions (essentially being permanently chat restricted).
The only way to improve the behavior of someone unaffected by their chat restriction is to increase the penalty to something worse, and ultimately remove them entirely if they continue to be a problem. That is why Riot is not looking for any way to keep toxic players in the community and does not consider permanent chat restrictions anymore. Of course, policies can change, but there's no sign of that happening anytime soon.
http://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/q7NYtdkw-uplift-my-permaban?comment=0003000100010000000100020001
If you have some sort of condition which makes it more difficult to refrain from taking out your frustration in chat you should consider getting help and talking to your family about it, but otherwise it would be a good idea to take measures to prevent yourself from typing, such as moving your chat window off the screen, using a 3rd party keyboard app to rebind your Enter key, or editing the config file to shrink the chat window down to nothing. If you're feeling frustrated, don't queue up for another game just yet! Take a break and cool down and come back when you're feeling composed.
