To put it bluntly:
Deal with it.
If you want to lose weight, and need to cut your calories, thats about all you can do. If you are eating twice your daily requirements, cutting back your intake by half is going to suck.
The human body is realtively unintelligent, and if you've trained it to expect a large amount of food throughout the day, it will be releasing hormones (primarily Ghrelin) to help your body process the food as it comes in. As you stop eating as much, your body will for a while still produce these hormones in the expectation of food. When it doesn't come they interact with your body in various ways, including stomach grumbles and pains, low mood, hunger, etc...
Along side this, the stomach can expand to accomodate a large volume and over time will remain stretched. So again, if your stomach is expecting a certain volume of food, it will squeeze against this lack of food and leave you feeling "empty".
Fluids spend relatively little time in the stomach when ingested, and are either quickly absorbed or quickly passed through, meaning they do little to promote "volume". Eating high fibre (both soluble and insoluble) foods can promote bulk in the stomach and digestive tract and may create a feeling of fullness for longer. However, if you need to half your intake, you are still not going to have that fullness you are used to. Additionally, the happiness you are feeling is probably coming from the consumption of sugars and fats. If you are eating less, you will generally have less sugar and fat, meaning you won't get this happy feeling. Drinking more water won't help with this.
You need to realise that you don't need as much food, and for a short time it will be hard. You can drink water or tea or coffee (black), to add volume, but the lack of calories will for a while suck. Yes, I've repeated that, and I'll keep repeating it. Weight loss sucks. I know it, and you'll know it too. While it is as "easy" as eating less, sometimes the feeling of your body rebeling against this drastic change sucks.
But realise that as long as you eat a healthy amount, you aren't starving, you aren't dying, so while your body adjusts to its new normal, just learn to...
Deal with it.