When you practice lucid dreaming it is very important that you feel confidence in yourself.
Take it as a fact that you are going to become lucid sometime in the future, maybe even tonight or in a couple weeks.
Get rid of any skeptical thoughts like "I don't know if I can make it..." and replace them with "I look forward to lucid dreaming, and I will achieve it".
This is true for any skills, actually - if you desire to learn something, then simply think to yourself "I will learn this, here I go!" and ignore any irrational doubts.

Also, make sure you have some concrete plans so you have something to look forward to.
A "lucid dream" shouldn't be a goal per se, instead your goal should be to wanna experience something in a dream, and associate that with being in a dream.