"Setting off towards happiness" is a common phrase in Chinese, often used to encourage people to pursue their goals and aspirations. The phrase doesn't have an equivalent in Engpsh and is a direct translation of the Chinese. Here are some example sentences in Engpsh with the Chinese translation:

"Let's set off towards happiness and chase our dreams." (让我们向快乐出发，追寻我们的梦想。)
"She set off towards happiness by quitting her job and starting her own business." (她通过辞去工作，创办自己的生意，向快乐出发。)
"He sets off towards happiness every day by doing what he loves." (他每天通过做他喜欢的事情向快乐出发。)

The origin of this phrase is unclear, but it may be a cultural idiom that has been passed down through generations. It is often used as a motivational phrase and encourages people to follow their hearts and pursue their passions.