Two very important principles I learned from the books of Rav Nahman from Breslov

Try never to be in debt and never to ask favors from people. Never to be in debt is a very important principle. 
I recall That i picked these up from the book of Rav Nahman called Sefer HaMidot.

The idea of not being in debt I recall had to do with repentance. That is--he said that if one wants to repent he should be careful not to be in debt.

The other principle I recall came from a statement in the Gemara in Yoma.