In private prayer we have a far greater advantage as so the exercise of our own gifts and graces and parts that we have in public...in public duties we are more passive, but in private duties we are more active. Now, the more our gifts and parts and graces are exercised, the more they are strengthened and increased. All acts strengthen habits. The more sin is acted, the more it is strengthened. And so it is with our gifts and graces; the more they are acted, the more they are strengthened.

The Secret Key To Heaven, 1665