Olive my 5yo has been driving us mad! She seems to have regressed and is competing with her 3yo sister. For her we have had a few at home pj days as she is exhausted and a bit over hyped about finishing kinder and starting school. I have been trying to spend a bit more focussed one on one type stuff with each girl. Tricky but really trying to carve out some differences as individuals for them. Dh has had to help and we have split the girls up a bit more than usual for Mum/Dad time.
My other ploy has been to get some time out! I have been trying to walk in the am so I feel less like the walls are closing in. I have also been lucky enough to catch up with friends who have kids the same age which has reassured me it is normal. Good luck!