Yeah, I agree with the TruBluLew. That's what happened to me in season 3. I got placed s4, then I went on a losing streak and dropped to s5. Then, I found myself struggling to win. It took me a while to realize that I wasn't winning not because of bad teammates or smurfs, or even trolls. I was losing because I sucked, and the fate of unskilled players is loss.
So, I proceeded to read a ton of guides, watch videos, streams, and practice with friends who I knew were good. I soon gained the game knowledge and mechanical ability I needed to carry myself throughout the ladder this season, and carried myself from bronze 2 to gold 3. I highly recommend getting good before trying to tackle the ladder, because the ladder is supposed to be reflective of your skill, not the other way around.
Try watching a bunch of people like foxdrop, gbay99, and the leaguecraft lecture series. If you haven't already, memorize every champion's skillset and what roles/builds they can do effectively. Also, try to be mature about things that go sour in games. Don't flame your teammates for making mistakes, and try to recognize what you could've done better, because most of the time bad things happen when multiple people make mistakes. And last but not least, enjoy the climb! If you're getting stressed out, then take a break. This is just a game, after all :P