Fitness/nutrition Rules are typically stupid and lack nuance. That being said here are some general guidelines that are easy to understand and if you implement them regularly, your life will be better as a whole:
Fitness -Don't go more than 48-72hours without doing some form or rigorous activity. -Make strength, power, and speed a priority. Your training should have you moving more weight, the same weight faster, or covering a given distance in less time on a monthly/yearly basis (based on training age). -Include purposeful movement each day. It doesn't have to be much, 5-20 minutes each day is ideal. This can be stretching, movement flow/mobility work, walk, jog, bike, paddle board, kayak, hike, etc. Just make it purposeful and do it often.
Nutrition -Consume 1 palm sized portion of lean animal protein every time you eat OR 2 palm sized portions of vegetable based proteins -Consume 2 fists of fibrous veggies each time you eat. -Consume 1 cupped hand up to 1 fist sized portion of whole grains OR starchy veggies OR fruit each time you eat -Consume 1-2 thumb sized portions of healthy fats at each meal (if your having a fattier protein source that can count as your fat too). -Consume calorie free beverages 80-90% of the time (water ideally) shooting for about 1/2oz per pound of body weight.
MOST IMPORTANTLY, do everything with purpose. Eat, Train, and Live with a purpose. Don't just go through the motions, that's no way to live and leads to sub optimal results, and an unsatisfying existence.