I started reading this book, Boundaries. It has a Christian focus, but I think it's equally helpful to everyone.
If you haven't heard of it, this book is all about our relationships with people - how to establish our boundaries. We want to be true to ourselves and be individuals when we deal with people, but we also don't want to to be overly rigid.
In general, I give too much of myself to people. Whether it's my time, energy, or just letting them in. I have to say "no" more often.
On a scale of 1 to 10, with 1 being no problem, and 10 being the worst, I'd say I'm at about a...7?
It's not really a large part of my vocabulary.
But it should be!