Two ways I know of to motivate yourself are sublimated anger and sublimated sadness.
To sublimate sadness, encode one of the following in your sadness.
“When will I become a Buddha?” (most difficult, highest motivation)
“When will I become an arahat?” (close enough for me)
“When will I spend the rest of my lives in heaven?” (least motivation I can approve of)
My attempt for Christians (untested possibly dangerous) “How can I attain the heavenly rebirth?”
To sublimate anger:
develop the anger, direct it towards a wholesome goal. clean up the mess.
This is foolish in the extreme in my opinion. It leads to ugliness, foolish mistakes where you think you are winning when you are actually losing and vice versa. It also destroys metta and generally makes happiness unatainable. It will motivate you for a while but the price is far too high.