Your thoughts and perceptions define the way you see the world, yo!
See it through rainbows, and everything will look lovely! See it through a black mist, and what do you think your life will be? A big ol' black mist of negativity.
Change your thoughts, change your life!
A worthy practice indeed....
One of the simplest ways that I try to change my thoughts is to say YES in my life instead of no. Instead of making excuses and whining, I try to reverse those negative patterns and wholeheartedly embrace whatever is in front of me by saying a big YES to it. It really helps!