It's not for me to say whether it's OK to feel resentment, I mean, we feel what we feel. But I do know it is not productive to wallow in it.
Examining our feelings can give us information we can use. I can get myself all sorts of worked up over the laundry list of things I can't do in life. Or I can get myself all sorts of busy doing all the things I am capable of.
When we first get clean we still have tunnel vision, what is life without our DOC? We have forgotten there is a whole huge world out there, and a whole huge world inside us!
Yes, we mourn our old life, perfectly normal, but even as we mourn, we build a new life.
My addiction cost me a great deal more than just not being able to use anymore. I am grieving a lost home, relationships, belongings etc, and that is normal and real. But even so, I do have a life that is full of good things. My time is more enjoyable when I focus on and enjoy those things I have, rather than wallow in sorrow.
Please note I said WALLOW. Feeling anger, resentment, sadness, etc is fine, healthy, etc, it's the letting ourselves get stuck and stew there that becomes the problem.
Acknowledge your very valid feelings, then move on.