Be thankful that you don't already have everything you desire.
If you did, what would there be to look forward to?
Be thankful when you don't know something, for it gives you the opportunity to learn.

Be thankful for the difficult times.
During those times you grow.
Be thankful for your limitations, because they give you opportunities for improvement.
Be thankful for each new challenge, because it will build your strength and character.
Be thankful for your mistakes.
They will teach you valuable lessons.
Be thankful when you're tired and weary, because it means you've made a difference.

Gratitude can turn a negative into a positive.
Find a way to be thankful for your troubles, and they can become your blessings.