When my husband comes home from work he sometimes complains that I have yet to shower (on days I had no time to do so). Most times I want to scream and say: "Yeah, right? Crazy!". Reality though, I have learned to just ignore it, picture my 'calm down' image of feather pillows being torn by a knife, and head upstairs to take the shower I, in my dreams, wished I had had time to take during the day.
There is no such thing as being 'just a mom'. But it can take a long time to realize that. Not to mention to reach the nirvana stage when you are actually content about it. I have had this conversation many times with my girlfriends, the ones who work and get paid and the ones who work (at home) but don't. Surprisingly none of them seem to have found a balanced formula (if there is one).
From where I stand (having worked both lives), is a matter of recognition, compensation and reward. Specifically, knowing where these come from to make you happy. As a 'just a mom' count the rewards in smiles, in kisses, in looking at your kid(s) go and thinking they learned that from you (and only because you were around to explain). Kids need the example and if you are around enough that example can come from you. I am not saying your kid(s) will not have other role models in life, but until they do it is kinda cool to be able to answer 'God in all of us and in all of the things around us' when your 5 year old asks out of the blue if 'God is coming back to earth' (specially if you are not religious like me it was nice to be around for this one).
As a 'just a mom' your work is going to be invisible (and unless you are doing everything a stay-home mom is doing this will be lost on you). You will not be praised for it (after all is kinda expected that you do what you do considering you are not holding a 'real' job). And, 'your' time will never be just yours (unless everyone is in bed - husband included - and you still have the energy to go about the things you wanted to go about when your 'daily to-do list' was too overwhelming for anything else).
When you make peace with these things you can rest (but just for a little while until it is time to fold that laundry). As long as you take that shower first.