The phrase "keeping on truckin'" typically refers to the act of persevering or continuing on with a task or journey, often in the face of challenges or obstacles. Some antonyms that could be used to describe the opposite of "keeping on truckin'" might include giving up, quitting, surrendering, or throwing in the towel. Other antonyms that suggest different variations on this theme might include stalling, hesitating, procrastinating, or dawdling, all of which imply a delay or lack of forward movement. Ultimately, the opposite of "keeping on truckin'" is any activity or mindset that goes against the idea of moving forward with determined effort and focus.