I once came up with an idea; an inflatible tent with a one way valve. You seal yourself in, then use a foot pump to inflate the whole thing, sucking air in from outside.
Not a great idea, in hindsight. But it doesn't need to be a "good" idea for long, for me to type it up and hit, Post.
Imagine being judged for it, 10, 20 years later.
Suicide is the same. It only has to be a "good" idea for 5 minutes; then it's too late to revisit in the cold light of dawn.