I'm 54 and have never been married or in a serious relationship.
I watch friends, who are couples, interact and I think how I would like some of that. I wonder what it must feel like to have someone waiting at home looking forward to seeing you. Over the years I've had guys be really flirty with me, almost on a daily basis (work acquaintances for example where we have become close) and when I have eventually revealed my feelings they have laughed it off like "oh I only see us as friends". So I just stopped putting myself out there because it eventually knocked my confidence.