system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why doesn't the intensity of the urge to urinate directly corralate with the amount of urine?

There have been times when I felt my bladder was about to explode and only a squirt came out.
gpt
Think of a bag which is being filled with water. The amount of water in it directly determines the amount of pressure on the walls of the bag. This is what you expect from your bladder as well, right?

Well, you are far more complex than just a bag. For example, psychological stress is also directly correlated to the "urge to pee" regardless of how much pee their actually is in your bladder. 

This means: Besides the amount of pee in your bladder, there are many factors influencing your urge to pee, nearly all of them are of a psychological nature.