Cliche and truism are closely related, but there is a difference between the two:
A cliché is an expression that is truthful but has lost its originality or impact due to overuse (e.g. “as strong as an ox”).
A truism is a statement that is so obviously true that it is often considered unhelpful or unnecessary (e.g., “You can’t have your cake and eat it too”).
While both clichés and truisms express ideas that may be widely accepted, clichés are overused expressions that have lost their impact, whereas truisms are obvious truths that do not provide new insights or information.