I just tried to do a 48-hour fast and only made it to 24 before I had to eat. I felt dizzy, irritable and couldn't concentrate on anything other than my hunger.
Stay busy, distract yourself with interesting things.
I have done 3-4 days water fast a few times out of curiosity. In my case, the hunger cravings diminshed after 48 hours or so.
However, I've never feel better, worse, or different from the experience. No extra energy, no extra ability to focus, no changes in sleep, no excessive fatigue, etc. Other than the hunger, I felt normal.
I am convinced that fasting is a fad and may have placebo effect if you think it will.
Addition: I have used a 48-72 hour fast as a precursor to a longer-term low carb/keto diet (for weight loss). The fast will get the excess sugar out of your system and you'll be able to get into ketosis quickly.
It will sound almost confrontational, but you literally have to force yourself not to eat. I'm not going to pretend it's easy, but that's the way to do it. The feeling will go away once you get past that stage of not being able to think of anything else but food.
I've found short term fasting to be like a muscle I have to exercise. Skipping a meal with abundant calories around me was hard. I had to start off small (skipping one meal) and slowly work up to slightly longer fasts (skipping the next meal, etc). I think we all have different physiologies and different mental adaptations (certainly for me hunger is partly an emotion, a desire to satiate that only bears a passing resemblance to how many calories my body needs) though and what works for me might not work for you.
If everybody around you feels as miserable, but they are not worried, it's way reassuring :) Bonus if you are in an isolated place making temptations hard.
Another thing is that you should avoid hard things in your first fast, such as working, reading complex material, filling administrative papers, etc. Take the time to rest, watch movies, listen to music, etc. The first two fasts I kept my job, and I didn't benefit as much as the next where I decided to take it easy.
Surprisingly, walking 2 to 3h a day helps a lot to feel less shitty, although you should not do it alone the first time you fast.
Once you are used to it, it does not necessarily because less shitty the next time. But you know what's up, and so it's easier.
One thing though, is that fat people and people with bad food habits will have a harder time.
Your body produces a hormone called ghrelin which controls your hunger levels. It produces it based on your eating patterns and the time of day.
When you fast, your ghrelin levels peak in the first 24 hours, but after that, they steadily decline. A lot of people don't even feel hungry anymore after about day three.
How do people make it past this?