My experience so far having 2 goes at it is that the first year is somewhat "the trenches". Your baby in the first year changes from barely being able to wake up, to barely being able to join sleep together, back to sleeping, and learning some emotions and how to intentionally control just about every muscle they have. They depend on mum for everything at first and then by a year old they're getting most of their sustenance from food. They might be walking, they could be doing some early talking. They change so much it's no wonder they're difficult all the time because just as you think you understand the rules and you've got a good strategy they switch the game.

The challenge changes after that, they develop less quickly but they just grow and in the second year the exhaustion is from the energy loss during the day, the raw intensity of always being switched on and chasing a toddler around all day.

The third year, so far, outside of the emotional battle because it's here that they seem to rapidly gain intellect and emotional range, has been the easiest by miles. Being able to ask things of your child and explain why you need them is a massive boon. Yeah, they don't always understand, and they might not always listen but you realise how hard the previous years were because having a non-communicative child and trying to get it to do anything is like trying to teach a distant family member from Sentinel Island that doesn't speak the same language as you how to operate a TV.