How do you know that people love you?
Because they're nice to you?
For all you know, they are just nice to you NOT because they love you,
but because they expect something in return, or because they just don't want
to cause trouble, or because it's just programmed in their mind that it is a
must to be generous to people. Perhaps they don't do it FOR you! They just
do it FOR themselves!

How do you know that god exists?
How do you know that you haven't been cheated?
How do you know that they can be trusted?

Problem is........... you will never know.
But........ what keeps them trustworthy is that you BELIEVE in them.
You BELIEVE that they love you, you BELIEVE that they'll always be there for you, you BELIEVE that they'll will never betray you.....