First I've talked to my wife multiple times about my end goal being FIRE. She is a bit wishy washy about the whole situation. Meaning one second she is like "Yeah that makes since and it is completely doable." And the next she is saying that the idea of retiring before we are 40 is ludicrous and not something she even wants to do.
This stood out to me, since I had the same issue... with myself! I'm single, and so the only person I have to convince is myself, and yet I still go back and forth.
It might help if you don't frame it so tightly into early retirement. Sacrilege on these boards, I know, but it might help. What I told myself starting out the most was this: the future is uncertain, and having a greater stash isn't going to hurt if plans change.
Things so far out can seem so uncertain, and some of us are worriers about all the what-ifs that can happen, and how those things could derail the plan and make everything moot. It might help if you, instead of focusing just on early retirement at a set date, focus on how trying to get there will help in the future by creating greater flexibility and stability.