Why did i have children?

So I have been asking myself in the last few days "Why did I have children?" Specifically, why did i have a second child after I had raised the first one? I have watched my normally happy, giggly, spirited 2 year old become a whiny, clingy, independent, demanding child! I still love her to death, but there are some days where I wish I could return her and get my money back. I went to Cancun with my husband a few weeks ago, and left my daughters with my mom and dad. Well, Lily (the 2 year old) had a cold and was sick the whole time, and since we came back, she has been clingy. This was the first time I had been away from her for more than a day, so I understand the behavior, I just can't stand it somedays.