Thank you all for your input, especially the folks who gave me good, thought-provoking comments.
temve and I have talked a lot about it in the past few days and we have agreed that this is the year for me to do it. It's going to require that my current procrastination level needs to go way down (and therefore my internet reading: but basically that means I'm going to stop reading huge WIP fanfiction that don't have beta readers and basically make me weep with frustration at the destruction of the English language and not going to abandon everyone here. In fact, my internet time will probably get more interactive - i.e. yes, the blog has a true purpose now)
We have also agreed that a reevaluation in March of this goal is a perfectly valid step and we can afford to lose half the registration fee if I feel it's too much for me and I won't be successful.
Some things to remember:
1) Sane decision making is not a sign of failure. It is a sign of sanity and adulthood. OK I need to say it again. Making an informed and appropriate decision about pulling out - AT ANY POINT - if I need to is NOT A SIGN OF FAILURE. IT IS A SIGN OF MATURITY AND THE CORRECT ATTITUDE TOWARDS A HOBBY.
2) Finishing an Ironman does not somehow validate me as a person, no matter how cruel the other kids in elementary school were. I do not need to do this to prove my worth as a human being. Conversely, if I don't finish for any reason that does not make me a failure as a person or even a failure as an athlete.
3) While I acknowledge that the race itself probably won't be a lot of fun (well, I think it will be fun until I lace up my running shoes and rather less fun from that point on) the training should be enjoyable, have intrinsic worth, and not be a major stressor in my life. If it is, that is probably a sign that I'm doing something wrong and I need to reevaluate and revise what I am doing.
4) Getting up early in the morning is necessary for the successful ironic athlete. Remember, dawn is beautiful.
A final note on Ironman: One of the things that attracts me to it is the same thing that makes
Waiting for Godot my favorite play and Camus and Ionesco some of my favorite writers. The utterly arbitrary nature of Ironman fascinates me to no end. The random distances, the specific order that they must be done, the bizarre and arcane regulations, the strange rituals at transition, the complete pointlessness of finishing as a middle of the pack age-grouper and paying for the privilege fascinate me to no end. I love the idea of doing this simply for the very sake of doing something so difficult and perverse. (Also, I'm a masochist)