What do you think of destiny - in practical terms?

How one small thing in one person (e.g. yourself) may change, direct and complicate lives of many other people? Like small argue casuing not choosing another person to marry / be partners? Or having / not having children? Or choosing one job over another? One person over another (in any sense)? Even, choosing where to go one day or night, instead of going somewhere else? May it affect the whole life? If so, then what's the practical, strategic approach to destiny? What do you think?