Taste the mango, adding more syrup or sugar (if using) until you're happy with the sweetness (it should be sweet, not sour). How much syrup or sugar you need will depend on the sweetness of your mango, or how ripe it is - adjust according to taste.
Note: At this point, you can strain the mango syrup if you prefer to get rid of any stringy mango fiber. (I actually prefer to leave it in, as I want as much fiber in my diet as possible!).
