too good to be true?

Such an old adage, but is it true? I won't deny that it can be a very useful saying when it comes to things like creepy car salesmen or the abundance of infomercials promising that their product will change your life. But if we always live by such a saying then we risk the chance of passing up the good because we think it's "too good to be true." Can't I just enjoy something good without having to worry that this old cliche will come to fruition?