Psalm 56:8

it will be different depending on which translation you have so I will type the ones I have for you

New King James version

You number my wanderings put my tears in your bottle, are they not in your book.

New international version

Record my lament list my tears on your scroll - are they not in your record

Revised standard version

Thou has kept count of my tossings put thou my tears in thy bottle are they not in your book

Personally I prefer the king James version but I included the others to be fair :o)

then I looked in my commentary and I found this

The heavy and continued trials that David's people have passed, should teach us to be silent and patient under lighter crosses.  Yet we are often tempted to repine and despond under small sorrows for this we should check ourselves.  David comforts himself, in his distress and fear, that God has noticed all his grievances and all his griefs.  God has a bottle and a book for all his peoples tears, both the tears for their sins, and those for their afflictions.  He observes them with tender concern.

I was told a very long time ago by a dear friend that every tear we cried was collected by God.  At the time I found it hard to believe because I was crying so many he would have to have a very big bottle.  I was told by many people that God wanted our joys and happiness and we should not cry or feel bad about things for God is a blessing of happiness and Joy and we as Christians should not feel bad because Jesus is in us.   In many ways I personally cannot agree with that philosophy Jesus is in us yes but we are still human and blessed with all emotions sadness and hurt included, the fact that Jesus is in us helps us to deal with that hurt and pain it doesn't mean that we wont feel it.  This verse by David in psalm 56 shows that God wants all of us not just the happiness but also our hard and sad times too.  We know that tears release emotions and make us feel refreshed like spring rain some people would say.  Tears can bring a healing to a troubled soul and refresh a tired spirit, by letting out our feelings we are releasing them to God

Sometimes God will move us to tears in holy spirit and cause us to weep over things, sin being one of these sorrow for others being another.  A song I know says weeping with our brothers and sisters in need, I have always found that a brother or sisters need and hurt affects me and in some measure we feel the pain they feel and are better able to pray.  As humans we are blessed with all emotions and God blesses with all things so tears are as valid as laughter.

Remember this though that God feels our pains he suffers with us in our darkest times we are not alone as we sometimes feel God is right there crying with us.  He is truly collecting our tears as each one of us is precious to him.