What makes prayer successful?

What makes prayer worth the while?

The effectual fervent prayer
of a righteous man availeth much.

Elias was a man subject to
like passions as we are,
and he prayed earnestly that it might not rain:
and it rained not on the earth
by the space of three years and six months.

James 5:16-18

If you are a praying person, what keeps you at it?

If you aren’t, what keeps you from it?