I'm assuming that Riven is the champion you were talking about after looking at your OP.GG.
Sometimes you get out of your groove after playing super well for a long time, I find I'm particularly proned to tilting if I'm doing really well, then have a few bad games, which then compounds upon itself to make me do worse and worse.
In doing very well you also can plateau as you begin to reach better and better opponents, the same things that worked in bronze and silver, are less successful in gold, referring to strategy and how you play.
Just take a breather, then get right back into it like nothing happened. It's difficult to do, but I've recently started taking things one game at a time. What I mean by that is ignore anything that happened in previous games. Don't assume something should work because it did previously, don't let a bad performance from last game make you play more passive out of fear of not performing well again. Riven in particular is a champion that needs to snowball, and if you play passively you make that much more difficult to do, and thus it becomes a self fulfilling prophecy where you're now performing worse because you're afraid if performing worse so you lose confidence in yourself. This is literally the mind set that I refer to as tilt.
