I had a 6 game lost streak recently, so I feel your pain. In 1 of those game I did bad I deserve to lose. In another I did so so, not bad not good, just very very average. I went even with my lane, kept them there with me, we both just farmed while the rest of the map was all hell break lose. Since I only did average, I deserve either or, so a lost is still expected. In the other 4 games however, I either won my lane or out jungle my oppentent. But the team either throws the game or just lose stright 1v1 or 2v2 duel repeatedly.
So I was frustrated like you. Did I deserve to lose all 4 of those games? No and yes. No since I out performed but I still lost. Yes since its a team game, it doesn't really just depends on me, it depends on the whole team, and sometimes its just out of my control how the team performs. Is my team have statiscally worst players due to MMR and RNG being harsh on me? Is my team just having a bad game? Is my luck just rotten that day? I don't know it probably is a bit of everything.
But I also remembered, there are winning streak that I just felt like I won cause my team are just really really good. It honestly didn't matter too much if I did good or not in those games. As long as I did not throw the game, my team would carry me.
So what the hell am I saying really?
These things just happens. Just like life, just like luck, just like chance, there is up there is down. Think no more on the matter, and you will get through it just fine.