The best thing I ever did to change my life from poverty and drug addiction to one of mental clarity and fulfillment was to begin the practice of MEDITATION. It is a regular part of my life now and I would say it is one of the simplest activities you can try in order to make significant change in your life.
If you're new to the practice I would recommend you start with some guided meditations. A common problem is that a beginners mind will wander all over the place, and then judgments of your thoughts, your self and your life will occur. Although this is natural many people believe that they are doing it incorrectly or can't do it at all. Guided Meditations are a good place to start so that a person can just focus on listening and relaxing.
Also, for the past year I've been experimenting with Isochronic Tones and Binaural Beats, to reach the calm Theta State of consciousness (the same state of consciousness people achieve while in deep meditation. By listening to different frequencies and tones, the audio automatically trains the brain to "meditate" on autopilot while simultaneously building new favourable neural pathways in the brain. Developing AND relaxing your mind simultaneously. It's never been EASIER!
Lastly, if you are to take your meditation practice more seriously I would recommend creating a space in your home to do so. Enjoy!