Obsession and compulsion are very normal characteristics, everyone experiences them. 'Focus' and 'drive' can be useful in any walk of life. But an extreme degree of these traits can be understood as
'obsession' and
'compulsion'.
Obsession
Thinking: The domination of thoughts or feelings by a persistent idea or desire.
Example: Feeling tense in a social situation, continuously thinking about the next alcoholic drink.
Compulsion
Acting: A strong, usually irresistible impulse to act on a persistent idea or desire.
Example: Feeling tense in a social situation, intending to limit the drinking of alcohol, but not being able to do so.
Some of us experience compulsion so strongly, it can feel impossible to moderate or control. Progressive consequences of these behaviours can have more and more of a negative affects on people's lives.