Sam2
Its not just about whether you have to be happy. By the way besides for Rav Nachman, the yesod vshoresh hoavodah says so as well he always says how evening and mitzvah should be done with simcha and enthusiasm. I STRONGLY encourage you yo get that sefer and learn it. It will open up vistas for you.
Its a matter of human nature that people tend to gravitate towards a life style that makes them happy. If Yiddishkiet is not doing that for you, you are living on shaky ground and you can Chas vesholem get attracted to a goyish lifestyle thinking that that will bring you joy.