Why do I always feel worse about having a baby at night?

This is our third night with DS, and it's been the same each night. It was the same with DD too.

The day he was born (Monday) was great. Yesterday was a bit hectic with coming home and inlaws to visit, and today was simply brilliant. DD dotes on him. He feeds well, settles and sleeps well. A trip in the car to the shops was simple. There's no crying or fussing or wind issues and family is beautiful and perfect.

Then 5pm begins to come around and I begin to get sad. I wonder why I chose this when our lives were so easy and perfect. DD is at such a great age, no more nappies, eating regular food whenever we do, easy to take anywhere, talking, sleeping through, generally being hilarious and such a wonderful little person. And now I've gone and turned her life upside down. All of our lives.

I had to leave her with Daddy to go to sleep because DS cried for a feed. DD cried because she wanted me there. The evenings are no longer our own when she's asleep, we have to tag team showers or eating and generally just go to bed early. I find myself thinking that things will never be the same again, we'll have to wait til DS is DD's age to get back what we had.

And it's not just my emotions that are different, it actually is different. Suddenly at night DS has wind pain and can't settle to sleep. He might want to feed forever, or he might just look like he does and need to pass wind so actually trying to feed him is useless because he won't take it. So the only option is to hold him. I'm ok with this, I will do whatever he needs, but when my emotions already change at night it's hard not to be sitting up, doing this and wondering if maybe I've made a mistake.

Like I said, our days are amazing and I love both my children with all my heart. I went through this with DD and don't regret a thing. But why do I have to get so sad at night? I hate feeling like this