Yes, I had exactly this with DS. I had a really big moment the other day where I suddenly realised that I could name specific things that I liked about him again.
4 is better than 3 and 5 is a huge improvement. The preschool age for me was just awful - no cute toddler quirks, lots of totally irrational stuff which makes no sense in any universe and there is no pattern to it, so you can't deal with it or pre-empt it either. They can be cruel, they are often annoying, they don't push the boundaries so much as drive steamrollers into them, and don't know when to stop. They like to make a lot of constant, unnecessary, irritating noise. They like to ignore you at times where this will make maximum impact and cling to your leg when you need to be left alone. They simultaneously think they are a newborn, worthy of newborn undivided attention, and a teenager, practically able to look after themselves except they can't use a toaster unsupervised.
I think it is worse when you only have one child.
My survival tips are:
Have a system to deal with bad/annoying behaviour. I don't care how hippy and AP you are, you need to pick up the 123 Magic (or whatever) because otherwise you will turn into a screaming banshee and then constantly feed into a cycle of irritation>react>overreact>guilt>shame>easily irritated due to guilt/overcompensating due to shame>leading to more overreaction, or more bad behaviour>infinite shouting, guilt, worse behaviour.
Keep it simple, consistent and black and white. You can reason and redirect again when they get to 5 or 6 - it's really not enough on its own right now (you can do it alongside the sanction system).
Look for good things - the 100 happy days meme on facebook is a nice one at the moment. Just think of one nice moment you had with them in the day. And yes 99% of "nice moments" you plan will get interrupted/ruined. Try to have a positive bedtime routine so you know there's one nice/calm moment of the day.
They are cuter through a camera lens or when they are asleep.
Try to think "He's not giving me a hard time, he's having a hard time"
If you have a husband/partner in crime, appreciate him!