Around two years ago, I tried devising a language for roughly this purpose. I concluded that it wasn't a worthwhile use of time; devising it is easy, but becoming fluent takes way too much time, especially since there's no corpus (or a very small corpus, if you use something like Lojban).
I write down and regularly review all my ideas, experiences, etc., and I've found it very useful to invent my own words (interspersed in normal English) for concepts that need annoying circumlocutions in normal English. I also use the derivational morphology of Esperanto and my own conlangs.
For an interesting example of a personal language created as a psychological experiment, see gjâ-zym-byn.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.