Your favorite "self development" book

Lately I’ve been fascinated with reading and listening to some self development/self improvement type books. I think so far my favorite one has been The Now Habit, which focuses on reducing procrastination and perfectionism. None of them have radically changed my life or anything, but I do like how they make you think from different perspectives and sometimes reading them puts me in a good frame of mind.
What books have you read that have positively impacted you most?

How I Found Freedom in an Unfree World: A Handbook for Personal Liberty

Harry Browne

The only “self help” sort of book I have ever thought was worth the paper it’s printed on is How to Win Friends and Influence People, which is amazing.

I haven’t read many, but some stand-outs:

Writing With Style: Conversations on the Art of Writing, by John Trimble

Seven Choices: Finding Daylight After Loss Shatters Your World, by Elizabeth Harper Neeld

How to Avoid Falling in Love with a Jerk, by John Van Epp