Can you tell if sake has gone bad?

Can anyone here help me discern if my sake has turned sour? I've heard that sake can lose its flavor over time, and I'm concerned about the bottle I've been keeping for a while. Is there a way to tell if it's still good to drink, or if it's past its prime? Perhaps through visual cues, a change in taste, or even a telltale aroma? Any insights or tips from seasoned sake enthusiasts would be greatly appreciated.