When in doubt, throw it out, but if a thing looks and smells and tastes fine it probably is.
But this assumes some experience. Like I know from experience that if dairy tastes fine to me, it really is fine. I will taste off flavors in milk long before it bad enough to make me sick. And sometimes dairy can last way beyond its use-by date. How cold your fridge is has a huge effect, but there is also much luck-of-the-dice around microbes getting in.
But something like, say, potato salad which might have flavors that vary and could cover up something going off... I will throw that out if it gets old or I've lost track of how old it is.
Does the tip of the bullet protrude from the barrel?