The phrase is derived from the Swahilian phrase "hakuna matata", which translated literally means "there are no problems", and the English phrase "fuck it".
:to quit or be done with something that was giving you worries or problems.
:to not put up with anyone or anything's (bull)shit or drama anymore
Hakuna Mafuckit is a wonderful phrase and a problem-free philosophy that promotes a very chill, laid-back, anti-dramatic type of atmosphere.
Josh: "This chemistry work is giving me problems man! What should I do?"
Dylan: "You're still doing that shit? I quit trying to do that shit a long time ago. I said Hakuna Mafuckit to it."