Of course, believing in yourself does not necessarily mean that you're happy, but it kind of comes naturally, happiness, if you feel proud of yourself, if you feel that you can do something without a doubt.
当然,相信自己并不一定意味着你就快乐,但这是很自然的情感,如果你为自己感到自豪,如果你觉得你可以毫无疑问地做某事,你就会觉得快乐幸福。