No one else can pull you up until you decide to stand. Krishna puts the responsibility squarely on the individual: elevate yourself by your own effort. Do not let yourself sink.
And then comes one of the Gita's most memorable lines — you are your own greatest friend, and you are your own greatest enemy. When you maintain discipline, put in honest effort, and stay on course, you act as your own ally. When laziness takes over, when harmful habits settle in, you become your own adversary. No outside force does this to you.
Consider a musician learning an instrument. Every day she practises, she builds something. Every day she skips, she loses ground. Nobody else is playing that instrument for her. The choice sits in her hands, every single morning.