I have a theory. We created laughter to protect us from things that are too much for us to bear.
I'm sure there's a word or a shorter phrase for the bolded part.
We created laughter to protect us from the unbearable.
1: involving, imposing, or constituting a burden : troublesome <an onerous task>
2: having legal obligations that outweigh the advantages <an onerous contract>
— oner·ous·ly adverb
— oner·ous·ness noun
Traumatic adjective: emotionally disturbing or distressing.
Trauma noun: a very difficult or unpleasant experience that causes someone to have mental or emotional problems usually for a long time
From: Merriam-Webster online
a bit much, insufferable, intolerable, enough already, last straw