I've hit a slump, what should I do?

I've been playing the game for a while and at this point I'm familiar with the basics. Lately I've been losing much more often than I've growing accustomed to and I'm not exactly sure what happened.

I primarily play morg and because I play blind, I often end up playing sup. When I do, I focus on pressuring the opposing laners, shielding my adc, and assisting them with kills and cs. Ahri, Illaoi, and Garen are other champions I have practice with and can generally stay competitive in randoms with. Sometimes it's evident that my team is less skilled than the other and that we've slowly been losing, but other times the loss results simply from being outplayed when objectives are vulnerable.

Throughout, I try to keep a positive attitude and work with the team; being negative doesn't help turn a loss around. It isn't uncommon for my assists to be one of the highest on the team and I spend a lot of time clearing minions when they pile up dangerously. It can be difficult sometimes, to assist multiple lanes when they're falling, so I focus on quickly clearing the casters and leaving the wave just weak enough to snowball our caster minions, then I move to the next lane or teamfight that needs help.

I think the matchmaker may have bumped me into a more skilled group of players than I usually compete with, or perhaps I'm just playing significantly worse than usual. Doesn't really matter; wins are more difficult to secure than in the past.

Any tips on how I can overcome unexpected losing streaks? How do you blow off steam during a losing streak?