II Corinthians 4:16-18
This is a very comforting passage for those who are experiencing difficulties in their lives.  It is comforting to know that God does not discount our sufferings.  He does not say "ignore them" or "you're making things up."  He realizes that human suffering is very real and difficult to bear.
It is also encouraging to see that our trouble is not in vain.  It is gaining for us a "far more exceeding and eternal weight of glory."  There will be reward for those who diligently and patiently endure hardship for Christ's sake.  It is comforting to know our suffering will not go unnoticed or unrequited.
Finally, it is comforting to know that our suffering is only temporary.  Even if we suffer until the day we die, we will suffer only for a period of years.  When compared to an eternity of perfection and joy, that will seem like nothing.  What a joy to know that it's only a matter of time until all heartaches are erased forever!