Sri Chinmoy suggests the following exercise to develop power in your concentration and to acquire power from your meditation:

When you want to get the power of concentration, identify yourself with the tiniest thing possible. Then only will you become all-powerful. God is all-powerful not because He is vastness itself, but because He is inside the elephant as well as the ant. God is all-powerful because He can be both elephant and ant. He is the infinite and He is the finite. Just because He is finite and infinite at the same time, He is omnipotent.

So if you want to meditate and acquire power, just think of Infinity itself, because there is God's infinite power. But if you want to develop power through your concentration, think of something very subtle, very small. (Source: Creation and Perfection – by Sri Chinmoy)

Don't be afraid of your meditation-power. Don't be a fool. It is your meditation that can and will give you the indomitable courage to conquer all your other fears. — Sri Chinmoy