Self help books...the best thing that every happened to me. Period. I've got sooooo much from them. If I had to recommend some I have a few that I've read multiple times.

Anthony Robbins - Unlimited Power & Awaiken the Giant Within
Richard Wiseman - The Luck Factor
Jack Canfield - The Success Principles & Chicken Soup for the Soul
Cynthia Kersey - Unstoppable
KellyMcGonigal - Willpower Instinct

Some give you exercises to do, I haven't dome the all but I did some of them and I can't even begin the measure the massive impact they've had on my self-esteem and my life.