Deep regret 🙁 day 4

Hi everyone. I have a tough situation. My husband and I have brought home a 4 month old mastiff/dane mix puppy from a rescue. We’re currently in a “foster to adopt” situation and I am strongly considering giving him back and feel like I made such a mistake.

My mental health is not ok. I think I was subconsciously trying to replace my other dog who we lost last year, and I am deeply grieving both him and our current resident dog because I feel like I took the one-on-one time we had with her for granted.

The day before we were due to get this puppy, my husband expressed reservations and I kept going anyway. Now he is more bonded with the dog and can see that he is an easy, good puppy and wants to keep him. I want to give him back. I so regret moving forward.

I don’t know what to do. I want to go back to when it was just the 3 of us with our current dog. She is mostly blind and we bottle fed her (she’s 5 now) and is deeply connected to us but is also doing well with the puppy. I also don’t know exactly how big he will get and I don’t want him to overwhelm her once he’s grown. Currently she does seem happy and is playful with him.

TLDR: I’m in a foster to adopt situation and would like to give the puppy back, even though he’s well behaved and gets along with our resident dog.