Sorry. I would like you to help me rephrase 2) because I'm not sure about its meaning. Thank you.I included a sentence for you to check.

1) I knew I shouldn't have left the apartment /I knew I should've stayed in watching TV/ If I'd looked at the moon and looked at my stars /I wouldn't be in this mess I'm in right now.
I should've known when my car would not get started.
2) It should've clicked when indecision reared its question mark. (???)
3) The experiment shows that we tend to judge people by the way they look.
I think we shouldn't judge a book by its cover.

1) I knew I shouldn't have left the apartment /I knew I should've stayed in watching TV/ If I'd looked at the moon and stars /I wouldn't be in this mess right now.

I should've known when my car would not start.

2) It should've clicked when indecision reared its ugly head.
I still don't know what "it" is, nor do I know what "clicked" means here.

3) The experiment shows that we tend to judge people by the way they look.
I think we shouldn't judge a book by its cover.