The big reason I became a SAHM is b/c it was what was best for our family. My husband's work is an extremely atypical schedule. In order for our kids to have any semblance of daily routine or stability, somebody needed to be available. Dad is the breadwinner, so that naturally made me the SAH parent. Which we like.
Even now (our kids are both in high school now) there are a few days during the week when husband basically does not even SEE our children. And he is home (not deployed with the military or traveling for his job). Deployments and traveling jobs I would imagine are difficult enough, but at least there are breaks to the away time. Husband's job (current schedule) requires that he be at work on Mondays well beyond the time our kids go to bed. And they leave for school the next morning before he is up (he works until 11 pm on Mondays and doesn't get home until almost midnight... EVERY Monday). Tuesdays, he works until 8 or 9 pm. Gets home around 9:30 or 10 pm. Most times, our son is already gone to bed. On Wednesdays, he leaves for work before the kids are out of the shower in the mornings. So he does see them for dinner on Wednesday evenings. But he goes to bed before they do, b/c he has to leave for work on Thursday mornings by 5:30 a.m. He gets home while they are at school, naps, gets up to eat, naps some more (the kids get home while he is still asleep) and he goes back to work around 9:30 at night until the next day.
For years, he worked weekends and wasn't available or at home for activities or events. He didn't have enough seniority to get those days off for almost 20 years. And he doesn't get holidays off. He is expected at work. He only gets things like Christmas and Thanksgiving off if they happen to fall on his regularly scheduled off days. Or if he happens to win the holiday lottery. He missed a lot of Christmas Days and Christmas Eves and Thanksgiving Days (and no ability to travel to see family b/c he'd have to work the day before and after as well).
So for a parent to be available to pick up a kid when sick, help with homework, supervise friends being over or taking/picking up ours, having any semblance of a family meal, or ferrying kids to after school activities (especially as they got older)... there is absolutely no way that my husband could do any of that. If I were working as well, I wouldn't be able to either. I'd have lost my ever loving mind, b/c he wouldn't have been any help. Not to mention that I wouldn't have much left over to be in a position to be supportive of his work schedule (which is terrible on his physical well being due to screwy sleeping hours and a high stress job).
I volunteered. Served on committees at church. Helped with programs or special events. Ran the Boxtops program at the kids' schools, complete with monthly special incentives for the kids to bring them in. I proctored a few classes for teacher luncheons. Chaperoned field trips. Got the kids to extracurriculars (karate, piano, confirmation classes, wrestling, mandolin, cross country, allergy injections weekly for 4 years, orthodontist trips).
At various times I participated in my own activities (women study groups, exercise classes/gym time) and now husband and I participate in a book club together. I stained furniture. Painted our walls. Dabbled in watercolor.
Down side? In 3 years or less, one child will be out of the nest, and the other will be driving herself where she needs to go. And now I've been at home for 17 years and my skills are completely out of date.
I should probably go back to school myself, or at least brush up on a few skills. Husband is looking at retirement in a few years, just as the kids leave the nest. We have an aging dog who's grown up with me home every day as well. (another thing I did... trained from a puppy 10 weeks old.) I worry how well she would transition (at almost 12 years old) to suddenly being home alone every day, should I take a regular job.
The first few years were the hardest for me. I thought I'd go stir crazy at home all day with an infant. Now, I see my son starting to spread his wings and fly away, and I wonder where all the time went.
There is no solution. Just do what works for you. You can find ways to stay busy. Take up hobbies (I started running, something I never imagined I'd do... but I did two 5ks with my teen daughter last year). Find a niche to volunteer. (I even take my daughter to play piano at the local hospice from time to time... she can't drive herself.)
But, if you can figure out a way to keep your skills up to date, I would do that. Keep your certificates up to date. You never know when you may want to go back to it.
My former career was in family law, and when I finally left and became a SAHM I realized I didn't want to go back into that. Too depressing. I was angry a lot. Not a fun field, and it left me very jaded.
So now I try to look ahead to how husband and I will spend time together when the kids are gone. We probably won't still have a pooch tying us to limited time on trips, so some traveling would be in order. My parents are aging and visiting them more frequently would be good, too.