I think it is safe and accurate to say internal happiness is dependent upon certain attitudes and other things (such as expectations in relation to others) we can either control or learn to accept, but happiness (as you have pointed out) is also dependent upon satisfactions of certain instincts, desires and ambitions that can only be filled by external sources (such as other people). Loners might occasionally learn to be content and "happy" even while alone, for example, but there is no such thing as self-fulfillment or self-validation amidst society as a whole.

I was a happy child because I was part of an active family doing many things together, then I began discovering loneliness and isolation as I grew older and realized I did not really "fit in" anywhere. I next developed certain attitudes and actions that seemed to work as coping mechanisms, but then those ultimately failed me as the loneliness and isolation continued to grow worse. Today I still feel much loneliness and isolation in relation to most people around me and I think I could live with that if there were no other options, but I am extremely grateful for my wife whose actions toward me present some validation I could never produce internally and who accepts my best efforts toward her (my sense of fulfillment in life).