When the Christian trusts, he is happy; when he doubts, he is miserable. When the believer looks to his Master and relies upon him, he can sing; when he doubts his Master, he can only groan. What miserable wretches the most faithful Christians are when they once begin doubting and fearing! It is a trade I never like to meddle with, because it never pays the expenses, and never brings in any profit —the trade of doubting.
– Charles Spurgeon