People who are too finicky about food, their immune system keep on going weaker and weaker. When something challenging is given to the immune system, it gets a chance to work. So now and then, once in a while, the immune system should be challenged. Then the self defence will come up from within. Otherwise being finicky gives rise to frustration and anger. Your system should be flexible and adjustable. And that can happen when you resolve mentally that the type of food you are going to eat won’t affect your system too adversely. That doesn’t mean eating unhealthy food. But that means not being too finicky about food and the quality of food. Choose a middle path.
Some people have this thing inbuilt in them that their body can adjust to any type of water, any type of weather, any type of conditions. People who are living in the slums, a their immune system is so much stronger than those who are living in bungalows. For you, you drink water which is not filtered. Then, for four days, you will be in bed. But those people, that thing shakes them. They are so strong. Our bodies can adjust to different climates, temperatures, and conditions. It's very elastic.