Thank you so much sir..

The two words are synonyms, and can be used interchangeably. However there is a difference in connotation. Destiny has more of a positive connotation, and fate has more of a negative connotation. 

For example: "It is my destiny to learn another language." vs. "I am terrible at learning languages; it is my fate to only speak English."

Destiny is more about your future as ordained by God or something, where as fate is more like being cursed. Make sense?