Happiness isn't some destination you reach. You might get something into your head that "Oh, if only I had this thing or reached this goal then I would be truly happy", and you may feel that way once you get that thing or reach that goal, but it's ephemeral. That happiness fades and you'll be confused and pining for the next thing or struggling to reach the next goal.
Happiness comes from being content with the way things are in this moment. That's not to say that it's not worth having ambition or wanting to improve oneself or one's lot in life, since stagnation is the enemy of happiness. However, you'll be happier trying to find the joy in little moments throughout your day or rejoicing in your own little victories than you will by setting some unrealistic goal that you can never obtain.
