It wasn't hard for me, we had always planned on me staying home while our kids were little, but I also wasn't coming from a real career, just working at various places on the Air Force base. I agree that you need to run the numbers, and see where you're willing to make cuts. There are positives to staying home, or cutting hours, financially. We don't eat out often because I have time to meal plan and cook. I'm not eating lunch at work, so we save there. My wardrobe consists of jeans and t-shirts, and I do lots of shopping at places like Ross and am also a big fan of clearance racks. My oldest is 6.5 and we've honestly bought very little clothing for either child...our families go crazy shopping for them, which is a huge help for us! And, of course, the biggest cost saver is no day care. I breastfeed and cloth diaper as well as do baby led weaning, so that all keeps money in our pockets. We don't take elaborate vacations, don't get to go home nearly as much as we'd like, and we are about to cut cable to add some more cash to help with this next baby, so it's not all roses.
And there are also benefits that aren't financial. I love that I don't miss anything. I've been here for every word, step, tantrum. I am able to take my oldest to and from school, I can attend every sports practice and game, I can volunteer in town and with my church. Of course, there are days when I want to find a hotel and just hide and sleep for a day. Or twelve. Staying home isn't easy, but I really do love it.
You have lots of time, and you might make a decision one way and then realize it wasn't the right decision for you, and that's okay. It will all work out.