Charles Spurgeons writings always have a way of dropping a bomb on my life, especially when it comes to prayer. In Lectures To My Students in his chapter on The Preachers Private Prayer he says:

How much of blessing we may have missed through remissness in supplication we can scarcely guess, and none of us know how poor we are in comparison with what we might have been if we had lived habitually nearer to God in prayer. Vain regrets and surmises are useless, but an earnest determination to amend will be far more useful. We not only ought to pray more, but we must. The fact is, the secret of all ministerial success lies in prevalence at the mercy seat. (Charles Spurgeon, Lectures To My Students, 49)