The problem with blaming it on your teamamtes is you're using them as an excuse for when you simply get outplayed or fail to recognize all your mistakes or teh times you screwed up as well. That is an easy excxuse to use yet the truth of the matter is it doens't old any water and is just a crutch. One of my friends who's Diamond or was last season is Large Snorlax and he'll tell you basically the saem albeit in a nicer format.
You'll get the idiot temamates for sure I've had them and the afker/dcers I lost my promo's back in S3 due to a few of thsoe but had my own share of mistakes and I couldn't carry hard enough to advance. I still ened to elarn my champs better and how to counter others as well as fix my reunes/masteries that I haven't updated yet really. I also need to play more SR but I've got a lot going on in RL so I don't do ranked currently.
I think the biggest thing to remember is don't go into a game with a negative mindset sicne if you go in expecting to se etrolls/feeders etc then tha't swhat you'll see regardles of whether that's true or not. If you're ona losing streak take a break and do something esle otehrwise that engativity feeds on itself.