It's difficult to gauge how much self-help books have actually helped me over the years, but I will say I rarely get discouraged. Was journaling today (ahem, why does this message editor think journaling is not a word?) and realized that by the time I was about 15, I'd read or listened to all of the following books/series of self-help titles that either my dad or my salesperson brother had bought over the years, including:
Every single thing Tony Robbins uttered or wrote
At least three books by Wayne Dyer (but probably more)
Stephen Covey's 7 Habits of Highly Effective People
Dale Carnegie's How to Win Friends and Influence People (I hated this book)
The Power of Positive Thinking by Norman Vincent Peale
A lot of books from Thomas Merton
The last "self-help" book I read was The Power of Now, by Eckhart Tolle. Actually, I've read or listened to that book now several times, and would recommend it to anyone.