I feel for you as I have the same problem not feeling guilty setting boundries and standing up for myself.

I wish I had a lot of great advice, but I really don't. I can tell you that people will respect you more when you say what you have to say nicely, but firmly and stick to it. It's funny how if people know they can push a person around, they will. It's just human nature.

Another really tough issue is that if you stand up for yourself, you might not be liked. At some point you have to decide if you'd rather someone like you at all costs, or not take advantage of you. I have a couple of relationships in my life that would be much, much better if I did certain things that I'm not willing to do so I have to live with these relationships being stressful. It's tough and I agonize over them, but at some point I can only do what I believe is right.

Here's a technique a therapist taught me years ago to help me deal with things that were bothering me. Draw two columns on a sheet of paper of your word processor and write 'distorted thoughts' on the left hand side, and 'rational thoughts' on the right hand side. Now under distorted thoughts write down what you're feeling--'everyone hates me because I didn't offer to pay for dinner last night when we went out.' Now challenge that thought--'they know I'm on a budget and can only afford to pay for my own dinner.' The goal is to bring clarity to the issue by challenging the misconceptions you're laboring under that are making you miserable. I can't tell you the number of times I've done this over the years and how much it's helped get cope with difficult situations where I felt like if I didn't do whatever, everyone was going to hate me. Give it a try...