I can totally relate to this.
Although, at least for me, I think it's a combination of the religion, and my family life... which in itself was a product of the religion. I have a really really hard time speaking up for myself. I have a tendency to let stronger personalities steamroll right over me, and I am always in fear of upsetting someone or making them mad at me.
One reason I live far far away from family is for this exact reason. I get a pit in my stomach when I think about being confronted by one of my family members. I could see myself lying rather than standing up for who I am now. It'll be seeing them next summer, and I'm already rehearsing my responses...
I have gotten better though, thanks to spending some time as an Independent Woman (no "attachments" for 2 years), and then marrying a Jersey boy. He's taught me a lot about ...er.... I guess a nice way to put it is... "assertiveness".