I ride alone a lot...up to 80 miles this year. I also find that it increases my confidence for the rest of my life.
I do a few things to try to be prudent, such as leaving a message on my brother's answering machine about which route I'm taking so that they would know where to start looking. I take my cell phone, but I often go places that don't have reliable coverage.
And, something that has made a big difference for me is that I have simply made peace with the fact that I carry a whole lot of cr@p that makes my rides heavier and dorkier, but contribute to my peace of mind. That includes a pump that is big and dorky, but that I can use if I mess up with my cartridges. It also includes a third bottle cage on the bottom of my bike. And, I always pack too much food.
All this came about because one time I had a cut tire and blowout 40 miles from home with few services around. I didn't have all that stuff with me, and although I gained confidence because I was able to limp home, it took me FOREVER, and I was tired, hungry, thirsty, and sunburnt. I decided I wanted to be more prepared.
Whew, this got long! I say go with what feels right to you, but consider that riding alone can sometimes give you a great feeling that carries over into the rest of life.
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury