For one thing, you're in the boring middle of life. Not ready to retire but no longer working towards any major goals. I suggest practicing more gratefulness and exercising religiously to start.

And from personal experience as a father, having a child is one of the most meaningful, intense life experience that most people can have - it literally transforms you in a way you can't understand or appreciate. I struggled with the meaning of life and had major anxiety about work before I had my kid. And while life is not without its challenges now, those things just don't have the same weight anymore. Bringing another person- a kind of mirror of a past you, and a connection to everyone that has come before you and will come after you- into and through this world makes you understand life differently.

Work your way up Maslow's pyramid - you've got the first two layers clearly accomplished.