I am in the exact same situation as 3rdGenCunarder described in her answer.
Originally I would have been making a trip to Lapland this week ( not a cruise) with a friend, but I broke my foot a couple of weeks ago, so had to cancel. That is when I decided to make a cruise to the fjords. This cruise is leaving from Rotterdam, which is not even 30 miles from my home, so very convenient. I will only book when my foot has healed enough that I can walk some distance without crutches or a walker.
Thank you all so much for your kind answers. It has given me a lot to think about.
But I already found one solo traveller on the roll call, so who knows how things might go.