When children come along, it is the woman whose life changes the most. For example, giving up work, a new experience of bringing up a baby for 10 hours each day 5 days per week. Loneliness, loss of self-esteem, reduced income, hormones all over the place etc etc.
The man carries on with his normal routine, ie going to work.
As Bunnyhop says, reaching 40 is a life changing event. It's a time for perhaps facing up to where your life is going, or not going. Do you have anything in common with your partner, apart from children. Much introspection with many questions needing to be answered.
I wish you well though and do continue to see your daughter on a regular basis and maintain a good relationship with her. Furniture is just possessions and can be replaced at any time.