When a prophet prophesies, he will also have at least two, if not all three of the revelation gifts in operation in his life as well. The simple gift of prophecy has no revelation involved in it. It speaks to men to edification, exhortation, and comfort. We speak to men, not God, when we prophesy. God speaks through us to men.
Comfort means to console.
If prophecy doesn't lift up, build up or cheer up, it's not prophecy. Timing is very important when bringing forth a prophecy. We must be obedient to give forth the prophecy at the proper time. This comes with much practice and sensitivity to the Holy Spirit. Despise not prophecies.