If you do currency trading
on FOREX, then great!

Keep on reading.

If you do manual trading then you should read some following advantages of automated trading:

...

SPEED!

A human could never beat the speed of a robot. Small delay in buying/selling may miss some good opportunities or it may results a good loss too.
...

NO FEAR NO GREAD!

A robot can’t experience fear or greed. Fear & greed is a very common problem with manual trading.
 
...

NEVER GETS TIRED!

As you know forex works 24 hours a day & 5 days in a week. So robot is best, because it never gets tired & never sleeps.
...

VARIOUS CURRENCY PAIRS!

A robot can monitor multiple currencies in same time, while it is very hard for human being to monitor & take decision on various currency pairs in all time.