Thank you very much. Any suggestions on this or other things people have done are greatly appreciated. I have not been playing all that long, but I did not come across anything in the rules where it states that a player can just decide not to play the effects of insanity.
Here are a couple of examples:
Pyromania: "You do not win the game as normal. At the start of your turn, if 6 or more rooms contain Fire, you immediately win the game and the game ends. If the game ends for any other reason, you lose the game."
One of a Thousand: "You do not win the game as normal. At the start of your turn, if you have a Bladed Weapon and you are in a space with exactly one other investigator, you immediately win the game and the game ends. If the game ends for any other reason, you lose the game."
There is nothing on the card or in the rules to indicate that this is at the player's discretion.
In separate games, our group has had both of these cards come into play towards the end of a Mythos phase (failed horror check causes a player to go insane) and the card's "game ending" conditions were already met.
In our "Pyro game", fire had been spreading on the other end of the map for several rounds. At the beginning the the investigator's phase, the insane player revealed the insanity and because there were already 6 rooms on fire, the game ended.
In our "Goat game", while it was a complete and utter coincidence, the player who went insane had picked up the only bladed weapon in the game and became insane, drawing One of a Thousand, at the failed horror check. He just so happened to be in the same space with one other investigator, at the time. At the start of the Investigator phase, the card was revealed and the game ended. Will this happen again? it's possible, but unlikely. Did it suck? You betcha! We actually had a pretty good chance at winning that game.
Our modification allows for the player to attempt to stave off the effects of insanity and gives the player an out should he fail the check. Again, if I missed something in the rules or if there are other ideas, I am fully open to them.