Hang on to (someone or something) like grim death British verb phrase
To grip, grasp or hold someone or something tightly because you do not want to lose it or fall
As soon as the branch broke off, I hung on to another branch like grim death.
The verb "hang" should be conjugated according to its tense.
A person who is completely unknown or has no connection with you
The guy I talked to at the prom last night is a perfect stranger.