Goin back to work-need reassurance/advice

So when I got pregnant I was doing equine physiotherapy on race horses (like human PT for athletes but on horses) and I did that until i was about 8 months pregnant and had to move home to have my son, I jumped straight into a nanny job that i worked until two days before I had him, then continued after 6 Weeks of being home with him. I worked that job 3-5 days a week, with him, until he was about 8 months old as the little boy I was watching was starting school. I then picked up a job at our family friends dog kennel which I was allowed to have him as well, he either napped/finished sleeping or played in his pack n play or I would wear him while I got my stuff done, the longest those shifts were were 4 hours. That job became very toxic as my boss and i were clashing she was making problems that weren’t otherwise an issue etc and it just wasn’t working anymore, my son was outgrowing his pack n play playtime and the tension between her and I was tangible. I had a talk with her saying it wasnt working for us anymore and asked to pick up less shifts the following month as I was working 7 days a week at this point , she agreed and it was clear that I wanted less shifts, not to quit because for one I don’t just abandon jobs, for two I still needed to work just every day was too much and I felt the less time being there the better our relationship may get because we wouldn’t be sick of each other. Well three days later she comes up to me at church and says hey I got everyone to cover your shifts your last day is sunday, very unprofessional and rude. I have a whole different set of beef with her but that’s besides the point. So then I was left scrambling for a job being a single mom with no help not even child support. So I managed to get another job nannying 2x a week from 530-930 not ideal but it’ll do for now. Then the family I am nannying for is opening a new restaurant and asked what other work I was looking for, and when I said really anything and told them my schedule they threw their arms up and are like you’re hired!! You’re exactly the person we’re looking for. Which is awesome, I definitely need at least something. The thing is, my son is 16 months now and ive worked since he was 6 weeks old, but I’ve never worked away from him. And I’m having a hard time wrapping my head around all the things I might miss.

So in an extremely long post I guess I’m asking how other mommas reason with themselves for missing moments we can’t get back? How do you work through accepting that? On average I’ll be missing about 15 hours of his awake time in the week now. Which is a lot it feels like. I know some miss more, but it feels like a hefty blow because that’s a large portion of his awake time that he has no parent around since I’m the only parent. I just feel like I’m doing him wrong, quality time is SO HUGE to me and I feel I may be cutting into that. On the latter he will get more quality time with his nonna and papa and auntie and uncle but still, how do you do it?