Hey, I believe you that you are just trying not to be rude. You're a very nice person, anyone can see that. That's why we want the best for you, because you deserve it!!
I just think you ought to reserve that softness and empathy for people who deserve it and toughen up the boundaries that's all.
Two excellent books I can recommend, that aren't marriage books, are The Gift of Fear, and Nice Girl Syndrome.
The Gift of Fear is must-reading for all women in my opinion, it goes into great detail how much danger women put themselves in because they hate to be rude. And we're socialized against it. But people die or get badly hurt because of that often misplaced feeling. I see so much of that trait in you and it gets abused. I have often been the same way. You know what, now sometimes people think I'm a bitch, but oh well. Usually it's when I have boundaries. (Occasionally it's because I'm a bitch. ;P )
Nice Girl Syndrome is very eye-opening about people pleasing. Which men can do as well, of course, but women also have the socialization to go with it, to never make waves or "be a bitch" which in a lot of people's eyes is simply standing up for yourself.
The hardest part about growing and learning how to have boundaries and self-care is that people WILL resist it, and tell you you've changed, or even that you're rude or whatever, but really that usually means you're not doing what THEY want.