Continuity mistake: When they finally arrive at the bottom of the sewer, Eddie's bandage is on a different cheek. (01:59:00)
Continuity mistake: When the Losers Club is in the sewers, the bandage on Eddie's face is on the wrong side in one shot.
Continuity mistake: After they find the club house Beverly tells Ben how handy he is. A bang of her hair is falling on her forehead. In the immediate next wide angle the forehead is clean.
Continuity mistake: When the Losers are in the Library, after killing Bowers. They call Bill who is at the funfair. It is night and dark at the funfair, but at the library, daylight can be seen through the window.
Continuity mistake: Mike's bandage is on the right arm instead of the left (and as previously mentioned, in the same scene, Eddie's bandage is on the right cheek instead of the left). (01:59:59)
Continuity mistake: The mug in the antique shop keeps turning around between shots. Check the painted symbol on it.
Answer: It's a bit involved, but the fact is that he was never that stable with the idea to begin with. He had forgotten all the horrors of his childhood (either due to the influence of Maturin the turtle [from the book] or Pennywise it makes little difference) and when it all started to come back to him, he panicked. And frankly, he had no way of knowing whether Pennywise could get him where he was or not. He didn't know enough to know one way or the other. But he knew that where Pennywise was concerned it would never be over simply. Pennywise would have tormented and tortured them like he did when they were kids, and when faced with that prospect he decided that ending it now, especially in his panicked state, was preferable to the idea of torture.
Garlonuss ★