It is part of Christian duty to endeavour to understand the nature of temptations. I would have you therefore to keep in mind that a temptation may go beyond the apprehension of the intellect, and take effect in the emotions and desires, and yet there may be no sin. For there are emotions and desires quite right and lawful in their nature, and only wrong in their degree or circumstances. The object which in this case tempts is presented to our intellect, and thence received into the affections, and taken pleasure in, in some measure or degree. The desire to take food or drink is natural and right. The temptation to seek it may pass from the intellect to the heart, so as to excite the desire for it, but if it does not pass the due limit, there is no sin. In David's longing for the water of the cistern of Bethlehem there was no sin; and he kept it within limit when he would not drink of it, because his friends brought it to him with the danger of their lives, but offered it to the Lord. This limit, both as circumstances and degrees, varies greatly, and depends much on our position and responsibilities. In persons who watch unto prayer, there will be ever a conscious perception of danger, when a temptation passes that boundary in our natural desires which it ought not to pass. So long as this is heeded, and the temptation to go beyond it is repelled, there is no sin. This may be a relief to some scrupulous minds, and encourage others to persevere in the path of godliness.
- text taken from Daily Bread - Bring a Few Morning Meditations for the Use of Catholic Christians by Father Richard Waldo Sibthorp