What does it mean when you are being told to 'think big'?

When someone told you to “think big”, it means that person is trying to motivate you to be ambitious. The bigger your goal, the more you can motivate yourself to achieve it. Example: To trade in a heavyweight world market we must think big.

When we say think big, it means aiming high to become successful and powerful. Doing something to materialize long term and short term plan.