Non-PRO English to Chinese Social Sciences Psychology history of psychology

The common cliché holds that “history repeats itself.” However, we may be closer to the truth if we assert that historical events are like snowflakes: Supposedly, no two snowflakes are exactly the same, although they may be similar. As we begin our sojourn through psychology’s long past with the contribution of Greek thinkers, it may be appropriate to apply the analogy of snowflakes to historical events.
请问上面这段话中“As we begin our sojourn through psychology’s long past with the contribution of Greek thinkers”这句如何翻译才恰当？我不知道sojourn在这里翻译成什么才合适。
另外，在第一句中“cliché”是什么意思呢？我只知道它不是英文，有没有朋友知道它的意思呢？

谢谢您的帮忙，祝您愉快！