Mellowing with every child?

Is it just me or it's a mom thing worldwide? I was always very worried with whatever my first baby did. It wasn't really funny. She is always testing new things, doing really, really daring stuffs. Those really get on my nerves. Jumping, running everywhere, touching and grabbing everything, you name it. And I was always so serious. Telling her that she can't play with it. Pulling her aside. Punishing her sometimes (oh how this breaks my heart afterwards). And being a toddler, of course she does it again and again. Until she remembers not to do it anymore. Now at 3 1/2 years old, she's brilliant. Always remembers to put back her towel on the rack after shower. Picking up her toys right after I told her. Oh, my baby. How you've grown up so lovely. Okay, these are not done without battles. We have our battles. Now my second babygirl.. she's a different story. As different as day and night with her sister. Calmer. More relaxed. An easy baby. And not just that.. whatever she does, it doesn't seem so scary anymore. Sometimes I laugh at the silliness of it. What used to scare me to bits, now they just bug me a bit and I brush it off. Is this normal? I mean, I'm trying not to be biased towards any child. But those things don't seem too scary anymore. I feel calmer. Like, feeling as if, what the heck, this isn't so bad. This won't hurt anyone. Or is it just me getting older? I must say being calm towards my new baby rubs off on her sister too. I laugh more at her antics rather than scorn at them, joins her sometimes; instead of telling her off, I twist the story so that it will turn her off it.. Yeah, life is better this way. I don't think I will love them equally because they are two different human beings, thus their needs are different. My prayers are always that I will be a mother that can raise them following the Sunnah (ways) of the Prophet Muhammad pbuh and be the mother that they need. I want to shower them with love and guide them with Deen (Islam). So that they will be safe and happy both in this world and the hereafter. My babies... What do you think? Is it possible not to be biased towards kids?