As you try different careers and relationship, you will end up with a stable ecosystem. The one where you go to office, do your work and everything seems alright.
Also, your wife is amazing, takes care of you and both of you seems pitch perfect.
When you are least expecting and not warning, a sudden stir can make your life worse. There could be arguments starting in your relationship and your job is making your life hard.
As such you would feel natural to be sad because so much has changed.
But the overall picture is that if you are going in phase, it will change too. It shall too pass. Enjoy the roller coaster even when it’s going up because it will soon go down.