Well, sure, if there's something specific I'm trying to accomplish, my degree of success helps me rate my rationality, but if my goal is to be as rational as I can, then I can still use specific tasks to help me gauge how rational I am. If my goal is to be as rational as possible, without anything else to protect, there is still lots of time pressure on me, provided I don't think I am as a rational as possible already. The more inefficiently I use my time, the poorer my final conception of rationality will be when I die, or on the off chance that i become as rational as I ever will be, then it'll take longer to get there then if I had used my time more efficiently.

I agree that solving specific tasks besides becoming rational, is necessary for becoming more rational. I just don't see why being rational must be instrumental for solving the task successfully, rather than my success in solving the task be a guide to becoming more rational. Again, lets assume I care a lot about being as rational as possible, or understanding rationality as best I can.