Inertia is the property of matter by which things which are at rest tend to stay at rest. Inertia explains why starting something new requires a lot of energy. A lot of force is required to begin moving a stationery object compared to the force that is required to keep a moving object moving.
Another property of matter – momentum – kicks in and keeps the moving object moving, meaning that you require less energy to keep the object moving at the same velocity. What once needed so much force to get moving, requires very little to stay moving.
The secret lies in momentum.
You need to keep pushing until momentum kicks in.