the only thing that I noticed that changed in me was my sudden understanding of what "fear" really is.
I had not experienced fear prior to becoming a father. The thought of one of my children being ... i'm not even going to say anything more. Use your imagination. That kind of thing scares me so much more than it did before I was a father.
One of our tech leads at work tried to do a team building exercise where we'd go around the table and name our greatest fear.
I was very glad to have been late to that particular meeting. It would have been pretty awkward for everyone if I'd started crying at the table.