I prioritise me, that's how I do it. Admittedly I do work from home, although full time. I work 10 days over 9. My day off I spend with DP. I have to go to court several days a week though and travel time can be 45 mins - 90 mins each way. Depending on the court I'm in. That does my head in at times as it seems like a waste, especially when driving. I do try to cycle commute, or take public transport. Then the travel becomes me time.
I'm an avid cyclist (I race). So I train between 7 and 15 hours a week. Cycling and racing is my headspace, stress relief, me time and something I do just for me. So I guess like socialising with friends perhaps?
I'm also elected to public office and am an active member of a political party. That probably takes 4 hours of my time a week? Again maybe like you could view socialising? It's something I schedule in and commit to and thoroughly enjoy.
I have an infant school aged child too. So I ALWAYS ensure I at least do bath time with him, have a snuggle and read to him. I also make sure he has my undivided attention the equivalent of one full day at the weekend. We always spend our hols together as a family too.
I feel no 'mum' guilt. I make a huge effort to have quality time with him.
In terms of socialising. I arrange a cafe lunch with a friend once a week. I also go to the pub once a week. I don't drink more than 2 pints, I'm home in bed by 10.30 (don't go out until I've done bedtime with DS) - I enjoy the social side.
No guilt felt anywhere! I do get tired from time to time, but I'll scale cycling back. Literally no guilt felt about putting my feet up when it's needed. I've never felt any. Even when DS was tiny and I'd go on my bike for a few hours. I've always had the philosophy and drive that if im not happy and if I don't look after myself - I suffer, my health and well-being will dip. Therefore family life suffers, I become shit grumpy mum and partner. Work suffers, I don't work well, can't think clearly and get stressed easily (work is very pressured and intense, my clients are very vulnerable).
I shan't waffle on about housework etc as that's already done. Our house isn't the cleanest, but it's always tidy and hygienic. DP certainly pulls his weight where that's concerned. We also share cooking. We do 5 school runs a week each.
Maybe it's a mindset? I did gradually move back to full time work. You've gone from 2 days to full time. Compressing hours into 4 days sounds very demanding. You certainly sound like you need to kick the guilt in the long grass and do stuff for you and accept everything else in your life benefits Literally doesn't matter what you do for yourself, as long as you enjoy it. Make sure you rank it as an equal priority to work/ family time.