Joy doesn't come from your circumstances, so it shouldn't affect your emotions much. Joy is totally different than happiness because it's one of the fruit of the spirit that develop by abiding in Jesus. (It's grounded cause it's a value)
 
In Paul's letter to the Thessalonians he said, “Rejoice always, pray continually, give thanks in all circumstances; for this is God’s will for you in Christ Jesus.”

So often, we seek God’s will for our lives, notice how he says rejoice & give thanks "in" all circumstances not "for" all circumstances. Again it has to do with the foundation because we're abiding "in" Jesus.

Jesus used the analogy of a vineyard to explain spiritual growth. He said, "Abide in me, and I'll abide in you. As a branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me." (John 15 / ESV) 

-Scott