As a chef of 6 years now working at a high level requirement in hotels around the country I will give you this tip: adding water will cut down the flavor so I suggest to avoid watering down a dish, sugar is a balancing technique we use to balance out most of our sauces, and I will explain why this works.
When a person's palate tastes sugar immediately the brain picks it up, you may not notice it but think about it the next time you have a coffee with 1-2 sugars, or ask a friend to make 3-4 drinks add sugar to one of them. The taste buds react with sugar/water in the mouth which sends a message to the brain "this is sugar". Not everyone likes a super sweet sauce so I suggest adding a small amount at a time and Taste, depending on how much lemon you have used you can cut it down a spoon at a time.
