I'm going to annoy alot of people with this bit of advice, I know it always annoyed me in the past. But the only way to hit the play button is to push yourself out of your comfort zone.
I was definitely stuck in a rut, not going anywhere. I'm now married to a lovely lady, but I had to move from England to California to be with her. It was such a struggle to reconcile making such a huge leap of faith into the dark, I've lost count of the number of hours I spent in mental anguish trying to choose between the easy life staying where I was (and had been since I was about 15!) and doing something I'd vever, ever contemplated before. I'm really glad I did choose to do something out of the ordinary, as far as I'm concerned: I have a social life that I never had before; we have a modest but cosy apartment; though the economic situation is tough, I'm feeling more confident than I have for a long, long time. Things aren't perfect, I still have trouble getting outside the front door, or doing some things that I don't feel comfortable with, but at least I've given myself the opportunity to change my life.
And to those in their early 20s: wait until you're approaching 30 before you start worrying about growing up. I was like that in my late teens and 20s, worrying that everyine else was living life while I was out of it. When I got to 30 and nothing had changed, I realised I'd wasted my 20s worrying, and should have just done things, or at least have tried to do things.
I know this whole post just sounds like the typical "pull yourself together and just do it" advice, but I promise you the effort is worth it.