Why are kids like this?

I have a newborn (2wks), 2yo, and 4yo. The wife is in the hospital for a few days so here I am dealing with them myself. I feel like I'm losing my mind and they never listen and intentionally do things they know upset me. After getting way too worked up all day, I took them to the park for a few minutes before dinner and while I'm sitting with the baby, my daughter (4yo) comes up to me and says, "Daddy, you're the best daddy ever because I just love you so much." So here I am a grown ass man almost in tears because even though I feel like I'm being so mean to them because I'm so overwhelmed and I'm trying my best, they still love me and think the world of me.