Climbing the ranked ladder, I've noticed that players in gold and below are just REALLY bad at closing out games.
Their thought proces looks something like this:
Oh we are ahead? let's do a teamfight that we will "certainly" win.
While it should be something like this:
Oh we are ahead? Let's focus on objectives and start pressuring towers. And let's not start risky ass teamfights that we could potentially lose and will probably throw us the game.
Even if I tell people this they still do it, and it's really starting to get tiring. So if you're gold or below, PLEASE! get yo ass on the internet and start reading up on stuff and how to close out games.
And yes I am a salty sailor :P
good luck on the rift,