There are any number of self-help books and gurus all telling you how to achieve this, but in the end it all comes down to the same answer: YOU. That's the whole story, really: you decide what you want to achieve and then you get on and do it. The worst thing you can do is wait for motivation to arrive, or think that you need some teacher or secret formula to get you started. Ask any successful person how they achieved their goals and the answer is more or less the same: determination, persistence.

You want to get fit? Then get up now and go for a fast walk, or jog if your fitness level is higher. You want to learn a foreign language? Buy a book or arrange some lessons today. Find a new job? Get your CV ready and start looking. And that's the answer: you can get tips like the one in the link above and they will help you, but you already have everything you need: you have yourself. Good luck.