It seems to me that tears serve to indicate how much emotion someone's feeling, but the presence of tears says jack squat about what that emotion actually is.
In fact, just for fun, let's make a list of all the emotions tears could indicate:
Overwhelmedness (is that a word?)
Also, a million more emotions that don't come to mind right now, as well as the infinite number of combinations that we can create from this list (because, I don't know about you, but I rarely feel just "sad" or just "happy". For example, right now I'm feeling "exhausted-melancholy-brave-optimistic-satisfied").
So, yes, I've been crying all morning.
But...goodness, I feel great.