What does it mean when your penis drips fluid?
What is that clear liquid that sometimes drips when I get an erection?
It means you became sexually aroused enough to trigger the Cowper's glands. These glands produce a clear, slick fluid that cleanses the urethra (the tube in your penis) of any remaining urine. Urine is acidic and will kill sperm, so the urethra is cleansed prior to ejaculation. The fluid also acts as a lubricant for the act of sexual intercourse.
The amount of fluid you produce will depend on how aroused you become and for how long you remain aroused. The mechanism that causes the Cowper's glands to produce fluids is independent of the mechanism that causes erections. Hence, you are likely to have an erection just prior to or while the fluid is being produced, but your body can produce the fluid without an erection.
The production of fluid by the Cowper's gland is an involuntary response. In other words, you can't control when it will happen. This can be embarrassing, especially if you happen to be prone to producing large quantities of fluid. Many men will produce enough fluid to leave a noticeable wet spot on their pants. The best thing that you can do is get out of situation that is causing you to be sexually aroused. It is likely that your mind is straying into matters where it doesn't belong anyway.