More discipline?

How can I be a more disciplined person? I mean i'm doing finein my life right now, but i wish i was more serious about some things. I tend to have a more cynical outlook and don't take stuff seriously. For example, i've been playing the piano for 12 years and i've always been decent. But i have never gotten to the point where I can make myself sit down for a good 1 or 2 hours and practice. This extends to all areas in my life; so how should I start taking things more seriously and not thinking everything is just not worthwhile and be a more disciplined person?