To add on to that, a lot of these discussions can boil down to one's locus of control. For those of you who don't know what that is, in a nutshell: having an external locus of control basically means you believe that your future is beyond your control and at the mercy of the world around you; having an internal locus of control means you believe that you're more or less in control of your destiny. Like Gemeos said, you can't control everything but you can control a great amount of it.
Numerous psych studies have shown that having an internal locus of control is very strongly correlated with happiness and success, for example:
When it comes to RuneScape, if Jagex releases a game update which is unfavorable to your playstyle or beliefs, a player with an external locus of control wouldn't change their playstyle to adapt to the changes in order to become happy or successful; instead they'd just spend lots of time getting angry at Jagex, hoping that Jagex changes the game so they don't have to change themselves. A person with an internal locus of control would change their playstyle and adapt to the game update such that they can go back to being happy and successful as quickly as possible. Keep in mind, however, that sometimes the best way to adapt to a game update is to either take a break or quit playing the game altogether. That's what I did when EoC was released in RS3, at least, and I'm extremely satisfied with that decision.