Confused? I Am a Traveler

In this era, most people only have three opportunities to change their destiny in this life: birth, college entrance examination, marriage... They are very worried. How can I help them? No matter what period it is, even if I existed before this star field was formed, what am I? I can be anything, because I am just a traveler... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.