One thing is sure with you: you don't have a problem saying no!
You're a nice person, but no-one messes with you, and just because you're kind doesn't mean you have to say yes to everything you're asked to do.
If you ever get the feeling someone is abusing your good nature, you're quick to tell them that you're no mug, thanks very much, and you're not going to do anything you don't want to. Your strong personality protects you from being taken for a ride and earns you respect.
All the same, make sure you don't take things too far. You could easily come across as selfish if you're not careful. Learn to say yes a bit more easily and try to be a bit more tolerant.