Are they synonyms?

Fate and Destiny

On a superficial note, they can be considered as synonyms but when deeply looked into, there is a huge difference.

Fate is the end of every event in our life whereas destiny is reached at the very end of our life.

Fate is controlled by our thought process whereas destiny depends upon our fate.

Destiny is achieved after a long tenure when it's the dawn of our life.
Whereas fate is every upcoming event.

Destiny is one final reaching point. Where there is nothing beyond. It all ends where your destiny lies. Whereas fate is ever-changing. With every new action, you can change your fate.

As said earlier, destiny depends upon our fate, multiple fates on a whole form a destiny.
The final ending.

Your success may temporarily depend upon your fate. But it's your destiny which defines whether you succeeded as a person or not.
                                                      - Vartika Saxena