It would be an understatement to say that life sometimes gets hard. Sometimes it gets stressful, people get on our nerves, and it seems difficult to find the calm in the middle of the storm. It sometimes seems that we can only find calm when there is no storm. Despite all of this, God's word tells us that we are to "Rejoice always!" The words "rejoice" and "joy" are closely related.
How can we rejoice when life is so difficult? This may seem like a "church answer", but it works: we need to seek God during the calm times in life, and even more when we are in the middle of a storm. This becomes difficult at times, but it is the way that we find joy in life.
Ultimate joy ultimately comes from Christ, and to find joy we must seek Him. Any happiness that we derive from anything else is temporary in nature, as God alone is infinite. The false joy that we get from the things here on earth is only temporary, since what is on this earth is temporary. To find joy, simply turn to Christ.