Why are some people so into there religion?

my grandparents came to visit, there catholic. I dont have a religion but congrigate in a lutheran chruch seens i was 14, i felt lke it was a calling seens i was addicted to drus and alcohol. I stopped after getting more and more into chruch, and the mage i have is, love God and your brothers on earth. I try to do this even dough i mess up alot, but they dont feel like im right. they dont know of how i use to be they just think i am a rebel of the catholic chruch, my grandmother doesnt stop telling i go to a fake chruch, that there not part of the romen pope etc..she even told me she was not coming to my weeding if i have it in another religion. they go house to house preashing off the lord, but and up talking bad about all other religions....what should i do?