To simplify grossly, an aeroplane stalls (that is, its wings stop keeping it airborne) when it goes too slowly.
It’s the same for projects: go too slowly, stop moving forward, and you lose lift. Try to climb without enough power or momentum, and you’ll find yourself falling instead.
Most stalls are easily recoverable – the pilot simply puts the nose of the plane down to recover airspeed, perhaps adding power from the engine, and the plane is flying again.
But stall low enough, or stall for long enough, and you’re in trouble.
Keep things moving. Get your angle of attack right. Keep the power on.
Maintain lift.
*Assuming you were high enough.