Human legends would have you believe that guardian angels are supposed to appear to you in big, extravagant ways.  They have to show you their wings, grant you a blessing, let you have a conversation with God, something like that.  However, those same legends show you why doing things that way is a bad idea.  You mortals get it into your heads that, just because we are assigned to you, you can use us any way you please.  You could use us for money or fame.  You could try ordering us about, making us fix your life.  In the end, though, everything falls apart.  We fail to perform at the shows you make of us.  We ruin your very existence, instead of improve it.  We even disappear.  Yes, we can do that of our own accord.
Instead, guardian angels show love to their assigned humans in small ways.  We’re the friendly baristas at your favorite coffee shops.  We’re the cute office clerks that always bring you donuts on your birthdays.  We’re your favorite music coming from who-knows-where, but, man, is that song catchy.  We’re the ones who drop money on the streets just so you can pick it up.  We love our humans in our very beings.  In fact, we care for our humans so much, that, when one of them dies, it can take weeks for us to feel whole enough to care for another one.  And we are most sad when our humans feel unimportant or neglected.  Because they’re not.  They’re just not seeing those who care about them, and how much they are loved and cherished.