Lost 10 placement games? HELP ME GET BETTER AT THIS GAME

So I haven't been playing League of Legends very long, as I started at the beginning of season 5. I leveled up to thirty, and I was so excited to start ranked. I did fairly good for a newbie, and I was placed in Silver IV last season. Now this season, I obviously really wanted to do ranked again. So I play my first placement game. I lose. No big deal. I lose a second, it's ok. I lose a third and I begin to think maybe I'm not as good as I used to be. So I begin to lose more and more placement games, and then I lose my tenth. I'm very frustrated at this point because I've probably spent qt least 12 whole hours trying to win placements. Every time it's either they have a better team, I mess up in early game, or my adc does, then the enemy adc gets fed, there's toxicity on my team or something to that affect. I'm VERY tired of losing at this point. I'm sick of it. can any one please give me any tips or tricks about how to get better, or at least climb the ladder.