It's hard to stop a moving train.
Or a bus.
Or a car.
Just like it's a lot harder to stop someone who's running than it is to stop someone who isn't.
Someone who isn't running, who isn't moving forward (or sometimes backwards) is easy to stop.
Easy to distract.
Easy to confuse.
And easy to convince to keep standing still.
To not start moving.
To not change.
That's why it's so important to keep moving.
No matter how fast or small you're moving forward.
As long as you keep moving, it'll be almost impossible to stop you.
P.S: The single biggest thing stopping us from moving forward are usually we ourselves...