Take a break, calm down, look at what you did wrong, try to improve, and then play another game with the experience of the losses behind you. Don't take your losing streak for granted, always look at ways to improve from them. Even if your entire team was feeding, think about how you could have countered it: owning your lane harder with better mechanics, ganking other lanes when you have the time, counter jungling and map awareness, effective play styles against this sort of team, etc.
Nobody is perfect, everyone makes mistakes and sometimes they deserve the loss, or even if they don't they will have made mistakes.
If you are failing to enjoy the game anymore, take a break. Sleep, work, schoolwork, anything other than LoL.