When a large ship wants to change direction it’s turning circle is quite big because it has inertia, or momentum, to keep going in the direction it has been traveling in. Our lives are no different. Our habits keep us moving in a particular direction and we have to work against that momentum if we want to change direction.
On the flip side, if you want to achieve something in life starting from a standstill is difficult and small barriers will prevent us from forward movement. For example, if a train is standing still you can put a one inch block in front of the wheel and it will struggle to move at all. If a train is going at full speed it can smash through a concrete wall.
Momentum matters. Building the right habits gives you that momentum. Doing the right things everyday will give your life an intention and a direction. We are what we repeatedly do.