It really all depends on what you want from life. If there is something you really want, then all the hardship and relentless hard/painful/boring moments you need to go through to get there will be worth it. When you don't want something, all the colourful descriptions of how wonderful that something is will leave you cold, because you just don't want it.
I hate going to the gym. I abhor it. i know exercise is good for me, but I still hate it. Twice I registered for 6 months and ended up going once or twice. I would find any excuse to not go. I didn't have time, it was too, late, it was raining, my exercising pants were not dry yet...
I love hiking. I find any excuse to plan and go for a hike. The preparation,. the exhaustion, the bad weather sometimes, the having to drive there and back... they don't bother me, because I love hiking so it's just part of the whole process that I love. My friends who don't like hiking find any excuse not to do it.
I am childfree by choice. I never wanted children, even when I was a child myself. I used to write lists of things I wanted to do in my life, and children were never there. I actually work as a midwife (not wanting children does not mean I don't love babies and children... I just don't want to take them home forever), so I am exposed every day to the life of parents. And there is not a single aspect of their life I want for myself. All the wonders of having children won't make me want them. All I see are the negatives. People tell me it's a wonderful experience, and I believe them, but it's a wonderful experience I never wanted for myself, so I'm not missing out on anything.
Women (and men) who desire children won't be put off by the nights of lack of sleep, the vomit, the poo, the constant sickness, the tantrums, the constant worry and fear for their well-being. For them it's part of the journey to parenthood, and the ups will always trump the lows. For me? Every time I go see a friend with kids I thank my lucky stars I don't have their life.