Almost constantly. It's actually gotten me into some trouble before. Specifically, I was cyberstalked by a former friend who was sexually and romantically obsessed with me for a grand total of over five years, at least partly because I spent the better part of a year leading up to me unfriending him everywhere not having the heart to say "please stop this, you're creeping me out and making me feel uncomfortable". (Now, granted, I was fifteen then and I've gotten a lot better at putting my foot down since then, but the point stands.)
Conversely, like a lot of you have mentioned, I come across as a total jerk when I get even remotely upset with someone...which has also cost me a few friendships. :/
Lately I've been getting a lot better at stuff like this, but it's still tough to find that balance of being nice without being (for lack of a better term) a pushover.
(On a somewhat related tangent...one of my best traits is that I'm incredibly loyal. It's also one of my biggest faults--when my friends fight, for instance, I feel incredibly torn, like I have to pick a side (even though that is, realistically, not usually the case). Again, this has led to a few irreparably broken friendships.)