Through my experiences, one of the most overlooked questions when considering success is defining what exactly success means to you. If you define success by monetary wealth, your goals and my advice to you would be very different from if you defined success as helping others, or having a family, etc.
While this definition will obviously change as you get older, it is still useful to stop from time to time and decide what it would mean for you to be successful. I would espouse more on my personal philosophies, but instead I will yield to those who are far better than me at conveying ideas:
Dan Gilbert TED Talk
and this one because I like it and it deals with handling success: