Time management with a little baby

I really love the concept of scheduling time ahead, putting everything on calendar etc. but I struggle with that. I have a 1 year old baby and all day is a lot unpredictable. I don’t know at what time will he wake up, if and when will he have an afternoon nap, how much or how little will he need me during a day etc. How can I plan my day? I have my own business, I want to exercise, cook, play with the baby, read and study…but whenever I put everything on my calendar, the next day always looks different than I expected. Then I feel stressed and overwhelmed (because I tell myself that I am behind and I won’t be able to do everything I wanted).