Being a single mum is great, you know everything is on you so don't feel resentful.
Sharing time with your child is horrible at first but honestly if you can maximise that time it can be the best of both worlds.
You can have time to relax, pursue things you enjoy, do adult things which wellbeing wise is great for you and balances out always being 'on' the rest of the time. Also do all the batch cooking and chores so that time with your DC is quality instead of having to juggle it.
Tips:
Have a transition activity when ever DC comes back, going from knee parent to another and different rules is tricky and can come out as poor behaviour. I used to run DD a bubble bath regardless of time of day when she returned, it helped reset her, then a baby / child massage to rebuild the bond and cosy clothes on and a warm drink a couple of biscuits and a story. That helps reset and rebond.
Keep the medicine cabinet stocked for you and DC and longlife milk in storage and bread in the freezer. If you can have a stock of food incase you can't get out due to illness for a week although with Deliveroo this is less of an issue.
Contact
Little and often, courts were happy for DD not to do overnights until she was 4 but this might be different if your ex is used to having her alone.
We built up slowly and then ex did twice a week 08:30 till 6pm, or after nursery until 6 pm.
Then Wednesday till 6pm and it was meant to be EOW 08:30- Sat to 6pm Sun but DD never liked sleeping over so he'd bring her back and pick her up in the morning.
He may well go for 50:50 and that will be hard but again it allows you to recharge and means you can prioritise your career and work on the non DC time so that is stronger, you can focus on health and wellbeing and your hobbies in the evening
Mothers/Fathers day and birthdays with relevant parent
Christmas and her birthday alternated, Christmas eve noon- boxing day noon, this was so she could spend uninterrupted time with both families, and was no bother as I don't work over Christmas so just made 27th Christmas eve and 28th Christmas day starting her advent calendar to coincide with that.
Only ever send old or cheap clothes you are happy to not be returned - it causes an awful lot of agro when the nice clothes don't get given back so just stick up on Supermarket or Primark basics.
Expect ex to provide everything when DC goes to his, don't start sending stuff especially things like prams you'll be upset if they get damaged.
Go through CMS for money, putting that middle person in place is really useful for disrupting the bad feeling. We do the middle option which has a small one off admin fee, they review his wages every year and send him a payment schedule to set up a standing order.