I meant to comment on this last week and am just now getting a chance to do it!
I'm in the same boat as you...sick of canceling plans when someone backs out.

So, I'm planning my first trip solo from October 22-26. I'm so excited!
Jennafoo --
This was always my dilemma too. My friends were getting less and less reliable with each passing year (they are not
as into Disney as I am), to the point of sometimes just backing out at the last minute or standing me up without a call or email! Or, they would show up and have to leave 2 hours later.
It was beginning to bum me out, make me angry and put a damper on my trips -- which is especially not fun when I am going for the holiday season or for Halloween Time, but it's not fun any time of year.
So I eased my way into solo DLR trips, gradually. I started out with a few golden solo hours in
Disneyland, about 6 years ago. It was weird at first, because it was so different from the way I was used to enjoying DL. I forced myself to get some solo PhotoPass pictures -- also awkward, but I did it.
Then, in 2010 I had a mix of "friend time" and "solo time." I had 2 whole days to myself, and I decided to just use that time to do what I really love doing -- which is take pictures and wander around without holding anyone up or worrying about what anyone else wanted to do! I loved having the PPH hotel room to myself, too! That was great! I decided to try a sit-down restaurant (Storytellers) alone, and that was a bit strange, but I made it through.
In 2012 and 2013 I had more and more solo time to wander around, taking photos (almost 4 full days alone in 2013, and 4 solo nights at the hotel) and exploring. I also decided to finally go on rides by myself. (One step at a time!

)
I am almost embarrassed to admit that I think I practically prefer solo trips now.

That's not to say that enjoying a meal, or silly PhotoPass pictures, or riding rides with friends isn't fun -- because, when the plan works seamlessly, it is extremely fun and we laugh the entire time. However, it all just seemed to be getting too complicated over time and I had to decide to either embrace solo trips and make the most of them, or never go to DLR at all. Fortunately I have embraced them and grown to
love my solo time -- I notice so many more details when I am by myself; I take sooooooo many more photos when I am by myself; and I find new ways to enjoy the parks, DTD and the 3 hotels that I wouldn't be doing if I had people with me!