It irks me so.
It is well-meaning but terrible advice. What makes it particularly vile, thanks for asking, is that it often comes from people who have held a very unreasonable newborn at 2 a.m. and should know better. And it's often directed at a mommy who is in a cloud of postnatal hormones that makes her feel... let's just say, a little raw, and who is quite overwhelmed by the everythingness of motherhood and whose back is sore because she hasn't put the baby down for hours and hours and hours and she just really needs a hot meal and for someone to tell her she's not terrible at everything.
Better advice would be "Let yourself enjoy parenting whenever you can -- try to relax and don't fight the sappy bliss, give into the sappy -- when you want to drop everything to hug and kiss your babies, DO IT. They seriously do grow fast. But in those moments you're not enjoying yourself, in those moments that make you want to crawl out of your skin to scuttle up the wall and hide in a dark corner, in which time appears to be standing still and you fear that gritchy little infant will NEVER let go of your tit, forgive yourself. It's okay. You're not terrible. It's hard!"
There's something so frazzling about enforced peacefulness. It's a special kind of awful.
Wee ones need us to be active sometimes when we're dead tired and need us to be still at times when we want to be active. It requires a sort of submissiveness that doesn't come naturally to me -- I doubt it comes naturally to anyone.
Everyone gets why 2 a.m. feedings are stressful. It's the 2 p.m. feedings, drenched in sunlight in a cozy chair that inspire lookers-on to assume you must be steeping in maternal bliss. It's that assumption that adds an extra level of "AAAAAAAGGGGGH" to it.
Human babies do come, after all, from human mommies and we can't enjoy every moment of it. We just can't. We're people who have been transformed into mothers and not into earthly projections of enlightened selflessness.
Maybe you are steeping in bliss. Maybe you're not. Every parent has visited both sides of that coin. Excepting, perhaps, Siddhartha Gautama who did transform into an earthly projection of enlightened selflessness after, mind you, leaving his wife and baby behind at the palace to embark on his spiritual journey.