I have been a single mom since my son was 3 and he is now 18. I have dated during this time period as I wanted to experience the gift of true biblical intimacy as God intended through marriage. It didn't happen for me and while I do not know the why, I'm so grateful God gave me the courage to not remarry for the sake being married as I saw so many friends make that mistake. As someone in this thread said, being lonely and alone is one thing but being lonely in a marriage is an entirely different level of loneliness.
I worked very hard and by the grace of God was able to earn an advanced degree to financially support my son and I. The Lord has blessed us but I still prayerfully wonder sometimes why I never found the husband of my youth. Scripture says it is not good for man to be alone yet not everyone is called to be married. Admittedly I still don't understand that. Seems contradictory yet I'm sure some who have a stronger understanding of the scriptures could shed some light on that.
I remain grateful for all my blessings and while I still have periods of sadness that I never experienced marriage, Im not lonley. I have wonderful family and friends to fill my life. I've made the mistake in my early years of being single of waiting to do X, Y, or Z until I was married and although it took me to long to learn I have moved out of that waiting period, years ago. I am very active in my church, have traveled some, have actively pursued hobbies, etc. I feel like I have learned to not only accept all the riches of the life I have been blessed with but embrace it and courageously walk it for Him.
I have my days of course where I feel cheated out of the riches of marriage, if I'm honest with myself and am getting better about laying them at His feet. I think those singles who are truly content with being single have realized that there really is so much more to living your life with Christ than marriage. It is one big slice of the pizza but not the only one!
I'm not 100% content but I'm working on it and can say that I enjoy being single and continue to look for the next challenge and adventure.