Don't get me wrong - I've always loved my kids, but the physical and emotional demands they put on you, and the relentlessness of those demands, are impossible to understand from the outside. My youngest was almost two before she slept through a full night, and the constant exhaustion had a profound effect on my relationship with my wife, on our sex life, on my health, on my whole outlook on life.
Children are not experiments, they are actual really real people who will live in your house with you for 18 years or more. You will love them, yes, and hopefully they'll love you, but if you think love circumvents everyday practical difficulties then you've never experienced it.
New parents - please PLEASE don't only listen to stories of how amazing parenthood is, or you may get the shock of your life (as I did)
(FWIW my youngest is 4 now, and I'm probably the happiest I've ever been - but who knows what teenage years will bring)