In nuclear physics, the term critical mass refers to the smallest amount of fuel that can sustain a nuclear reaction at a constant level.
This concept of critical mass can be applied to life. Critical mass can mean the size or number that something needs to reach before a particular change or development can happen.
Before your abs get toned, you need to run a few kilometers. Before you become rich your investments need to reach a certain critical mass. Before your business is profitable your sales need to reach a certain point. Before you become an expert you need a few hours of practice.
The important thing is to realise that there is a critical mass to everything. Our job then simply becomes striving without ceasing to reach the critical mass.