I have taken 4 cruises alone over the past few years, not part of any group--so truly alone.
I wanted to cruise, but could not interest anyone to go with me.
I am not a very outgoing person, and I will say that those solo cruises were difficult for me.
What helped a bit was asking for early seating at a large table, so at least I got to eat dinner with the same people every night.
On one cruise on the Brilliance out of Tampa two years ago, I found myself seated with a number of other solo travelers: The Maitre'D had made this arrangement on his own. On the second and third night, other solos were found and brought to join our 10-top. It was brilliant.
One of us then said "I'll be here tomorrow for breakfast at 9AM. Anyone interested?", and yes....
We were off and running.
So ask if there is a "solo" table on your sailing.