Being assertive and feeling guilty

[Guyintheback]

@last 3 repliers: That's a good explanation really.

I don't know why these things cause me so much trouble, when on a conscious level I know I'm in the right.
Probably has much to do with the way I was raised: When I look around in my family, all members, especially the men have trouble drawing lines and saying no to things.

I guess I have to push through that pain period if I don't want to end up a bitter man.

It's just very hard for me to figure out when it is okay to say no as I have neither experience to draw from, nor a role model to emulate.

Thanks for all the replies so far!