"If Christianity does not make a man happy, it will not make him anything at all." William Barclay in his commentary on Philippians.
And I would agree, except that because I do not wish to confuse the two things, I would say "does not make a man joyous, it will not make him anything at all." Joy can bring happiness, but happiness is not the end of joy nor are they full equivalents. Happiness is part of joy--and joy when joy overflows, a kind of happiness accompanies it. But we shouldn't expect so much to be happy as to be joyous.
Barclay was an enigma, wasn't he? I've spent many enjoyable hours reading his commentaries on the Gospels -- but haven't read his commentary on Phillipians. It's been several years since I've picked up one of his books -- I often got exasperated with him, but the wealth of knowledge and information in his books is compelling and his style of writing refreshing.
By the way, your commentary below on my favorite verse in Phillipians is excellent and has blessed me this day. God bless you.
...and I would agree, except to say 'does not make a man content' :)
God Bless.