[jodrellblank]

Speculation: Based on the principal that you can't improve what you don't measure (or, what you measure you improve), you could keep a log of the sloppy mistakes you make. After a while, maybe patterns will emerge and you can attack 'mistyping numbers' separately from 'missing cases in a switch block' and 'correct behaviour of nested-if took 5 attempts'.

[bodhi]

I was going to write exactly the same thing, but you've put it more eloquently than I could. Also, it would seem to me that just "writing more test-cases" wouldn't get one very far as the tests are going to be as sloppy as the original work.