They are not something that you prevent from being made in your body. They are automatically made when you eat food that is not automatically converted into calories. This is used for energy later on for you body.
But too much of triglycerides is bad for you. This condition is called hypertriglyceridemia. Your doctor can detect if you have this condition by simply running a lipid panel (a blood test) that measures your overall cholesterol, you LDL and HDL cholesterol, and also measuring your triglycerides.
If you do take this test, they will make you fast for about 8 hours. They make you do this because triglycerides are usually lowest after you fast but goes up really high after a big meal (like a Thanksgiving Dinner!).
(Extra: your triglycerides are measured in milligrams per deciliter (mg/dL) and if your levels are:
BELOW 150 -----------------Healthy
150-199 -----------------------Borderline
200-499 ---------------------High
500+ --------------------------Very High
Most people are under 200, so in the end, you don't have to worry about your triglyceride levels.
You can read more about it here: https://www.cardiosmart.org/Heart-Conditions/High-Cholesterol/High-Cholesterol-Home/Very-High-Triglycerides
Plants can make their own food by photosynthesising however, animals need to consume plants for energy/as food if their were no plants animals would starve. plants also provideanimals with oxygen as a waste product of photosynthesis which animals need to survive
