Your digestive fire, called agni in Sanskrit, is the energy you have available to process whatever you consume. It is the physical digestion as well as your ability to digest life.
Physically, this energy directs absorption and use of the nutrients that food has to offer. It also kills any pathogens in the food. If digestion is weak, then you will not digest well. The very best quality food on the planet, organic or not, raw or cooked, local or not... will not matter. Weak digestion also leads to an accumulation of toxins in the body (ama) which weakens your immunity.
These considerations suggest that keeping the fire strong will help prevent and avoid health problems. As you learn to be aware of your body, you will begin to know if you are digesting well.
Some of the results of weak digestion are: constipation, gas, low appetite, excessive appetite, sluggishness, poor circulation, not sweating, offensive body odor, bad breath, and weak immunity.
Some habits to eliminate or refine because they weaken digestive fire are: eating before the previous meal has completely digested, grazing and not chewing food thoroughly. Overeating at any one meal. Going to bed before you have completely digested your food (allow at least 2 hours before laying down). Drinking large amounts of liquids with a meal and within an hour after your meal. Eating while angry. Eating while standing up. Eating with loud noises or excessive activity around you. Eating large amounts of fried, barbecued, highly processed, or sugary foods. Too much sex, or sex within two hours of eating. Little to no physical activity. Excessive sleep.
Examining the state of your digestion on a regular basis to be sure it is in balance is an easy way to prevent disease. Most disease begins in the digestive tract. Correcting a problem in the digestive tract is much easier than when the problem has moved into other tissues of the body. See what changes you can make in your process of eating and see how you feel.