(Edit: wording)

I postponed the decision because I was afraid I might regret not having children (despite never having wanted them). Once I realized I would also definitely and repeatedly encounter feelings of regret for HAVING children if I did get them, I accepted that I shouldn't build my life around the fear of maybe having negative feelings. After that, it was smooth sailing through vasectomy and a childfree middle age.

For the record: I haven't regretted the decision, not once.