because he might forget it
The answer is a secret. You can have a secret, but if you share it, it is no longer secret.
A secret.
This riddle describes the concept of a "secret." When you possess a secret, there's often a desire to share it with someone else. However, once you share the secret, it is no longer just yours, and in that sense, you no longer "have" it as a secret.
a secret
This riddle describes a secret. If you want to keep a secret, you must keep it to yourself and not share it with others. However, once you share the secret, it is no longer just yours, and the essence of it being a secret is lost. Thus, sharing a secret leads to its disappearance.
its a secret
A secret
secret
A secret.
It's secret
Not necessarily. You could only share some of it, or maybe share it in such a way as to retain ownership.
The answer to the riddle is "a secret." When you have a secret, it often creates a strong urge to share it with someone. However, once you share it, it is no longer a secret, and you lose that exclusive knowledge.