Take good care of your teeth. It will save you years of suffering and grief, and thousands of dollars if you do.
Listen to your parents when they suggest careers, but if there is a career path you love, make a plan and follow it. Think about careers that make a good living, but don't involve 4+ years of college, like plumbing, electrical, HVAC, commercial trucking, hair dressing and barber school, auto and truck mechanics, welding, and any other trades. A good tradesman can make a ton of money, have no student loan debt, and there is a lot of need in all those jobs. People who work in the trades are retiring in great numbers, and there will always be jobs in those fields.
Do what you say you are going to do, and be there when and where you say you will be there. Especially where your job is concerned. Finish what you start. Ask questions, including asking for help when you need it. Make good friends at work - you are going to be there a lot.
Enjoy your time with your grandparents. They won't be around forever. Neither will your mom and dad.
If you get a great job, don't spend all your money on an expensive car, a ton of electronics, and going out to eat. Try to stay away from debt and that includes running up your credit cards.
Be a nice guy and a good friend. Find a hobby that will give you the opportunity to meet people as your grow. As you get older it is harder and harder to make friends, and your older friends will move and drift away.
Have fun when you can. I wish I could do everything all over again.