Sense of humour is a kind of self-defence against the worst happenings we are obliged to cope with.
Humour, self-irony and logic...
They are like a thick armour which can spare us some of the effects of life hardest strokes.
People, who want to be funny on purpose, usually are not, they might be grotesque, but not funny.
I don’t know why, but people who can be naturally humorous and self-ironical are usually apparently very low-profile, they don’t look funny at the first sight, they are often misunderstood, as if the gift of humour was so precious to be kept deep inside and showed in not too massive doses.
What is funny must not be foreseeable.
It must be unexpected, not planned, and it must be limited in time, not repetitive, in order to not loose its force.