Myopia can't be cured by wearing glasses or not .Glasses are used to help you see better,they can't change anything in your eyes. But as your prescription is -6.25 ,it is better for you to wear them ,otherwise your eyes will be forced to see clearly and cause eye strain and fatigue easily . Also ,if taking off glasses really work ,then no one would need glasses.You can only cure your myopia by lasik surgery .
Unfortunately there is no cure for your myopia and it will not get better with or without wearing your glasses, doing eye exercises, eating carrots, sweet potatoes, or any vitamins. You are nearsighted and will be nearsighted for the rest of your life because your eye is to long and doesn't focus the image correctly on the retina; all your glasses do is refocus the image so it focus's the image correctly on the retina. Once your vision stabilizes when you are in your 20's you can opt for vision correction surgery that will basically use a laser to flatten your cornea so you can see without glasses. You will still be nearsighted even with the surgery because your eye will still be to long and have to have your eyes examined just as you do when you had glasses to rule out any retinal problems that come with being moderate to high myopic.