Inevitably when someone is expecting their first child, they get a lot of advice from other parents. Much of it is useless – get your sleep now! You won’t sleep when the baby comes! – but if you’re lucky, some of it might carry you through some rough times.

After four and half years of frankly harrowing parenthood, my advice is this: comparison is the thief of joy.

When Bea was born, I bought myself a copy of What to Expect: The First Year. In no way do I mean to disparage this book; it was an excellent resource during those first few months when I worried about everything and anything. But it has a fundamental flaw: it’s organized according baby’s developmental milestones throughout their first year, with summaries of what baby should be doing by what week or month.

I checked those summaries religiously in the first six months of Bea’s life. At first, everything seemed fine. Bea was a happy, healthy little baby girl, and there wasn’t much to concern myself with. But when physical developmental milestones came due, like holding up her head and rolling over, the anxiety took over.

The designated week by which she should be able to hold her head up came and went, and Bea was still pancaked on her play mat. When she was finally able to lift her head and keep it up for any length of time, we were honing in on being able to roll over. That one, too, came and went without Bea being able to so much as roll to her side.

I was a mess of anxiety. Were we doing enough tummy time? Was I holding her wrong to breastfeed or cuddle? Maybe I should have held her upright to soothe her – except doing that always made her angrier. Was it something I was doing wrong?

In retrospect, it was none of those things. I know now that guidelines are just that – guidelines, based on aggregate data and not on individual children. No teacher looking at a fourth grade classroom can tell you which kids were early to walk and which were late.

Bea, it turns out, was just a lazy kid. She has never met a developmental milestone she was inclined to meet. She rolled over late, sat up late, crawled late, walked late.

When she was six month olds (and finally rolling over, thank goodness) I put my copy of What to Expect away. I’d spent so much of the first six months of Bea’s life stressing over what she should have been doing that I missed what she was doing.

By the time Bea was two and George was born, I was much better as letting the milestones coming to us rather than trying to get us to them. George, too, was not an early developer, but this time, I was able to let go of my worry and enjoy watching him meet his challenges in his own time.

By the time George was 17 months old, he had been “kneeing” it around the house for two months and tearing out all the knees in his pants. We’d encouraged him to get up and walk, but so far, he wasn’t interested. I shrugged it off and bought iron-on patches for his pants (if you really want to know, yes, a determined little boy can also tear out patches in his mended pants, too).

That Easter, we took the kids over to my parents’ house for Easter dinner. All my siblings and their kids were there, including George’s cousin Henry, who was born just four days before George and who had been proudly walking for a few months already.

George sat on the carpet in my parents’ living room for an hour or so, watching Henry walk by as he played. And then, without any fanfare (and surprisingly little effort), he got to his feet and walked off to follow him, and never looked back.

Two years before, I’d have agonized comparing George’s progress to Henry’s. It would have worried me to death wondering why my son couldn’t do what his cousin could. But on that day, I’d already let go of my worry over when he would take his first steps. And in doing so, the joy of watching him proudly march across my parents’ living room was so much sweeter.

So, if I could go back and give myself the advice I didn’t know I needed before Bea made us a family of three, it would be this: every kid does things at their own pace. Take it one day at a time, and enjoy where you’re at today, because tomorrow, it will change. And in the immortal words of Bluey: Just run your own race.