In the simplest terms, I suppose what I'm looking for is just a "quote of the day" generator. Albeit, one that I can put my own quotes into.
I have what I jokingly refer to as an "operating manual". Essentially it's just a constantly-updated evernote that contains rules for how I want to live (eg. "No drinking alone"), reminders about myself (eg. "You always feel better after exercising"), and my philosophy about aspects of life (eg. "In the news media, misery and controversy sell better than joy and harmony").
I'd like to be able to receive bits of this "wisdom" throughout my day, ideally by way of some sort of notification on my phone. Does any such app/service exist? Bonus points for one that is open source and cross-platform!