It is impossible for anyone to actually know their purpose in life, if there really is one. We can surmise, and guess, based on our dislikes, or likes, but no one can ever be certain there is one specific purpose for them.
It is therefore, imperative that we have some conscious purpose in life. That too is dependent on what we like, or dislike.
Everyone has different interests which is great, otherwise there would be an over abundance of crooked lawyers and not enough auto mechanics.
If we follow our hearts and find a purpose that is worthwhile we will be guided in the direction our life needs to go and grow in.
I doubt if anyone is actually born to be something they hate as a destiny, but then that prospect is relevant as well.
If one believes in Karma, then to live a life that is harmful and hurtful to others, one would expect that that person would (should) be reincarnated in the opposite role to learn and understand the pain that their nasty attitudes, and deeds, actually caused to the people they afflicted.