How do you protect yourself from the sun?

The sun was suddenly elevated to the status of an enemy about 15 years ago. Even though it's been considered the source of life for centuries. What happened? Why did the sun fell into disfavor and we suddenly need to urgently protect ourselves from its rays? Protection from the sun should be dosed. The use of sunscreen must be very careful.
The sun is not an enemy, but a friend, because it delivers vitamin D, which is important for the body. Therefore, if you constantly apply sunscreen, you will develop a vitamin D deficiency in your body, and this can even lead to cancer.
How to find the golden mean to come back from a vacation, on which hundreds of thousands have been spent, healthy, with a normal level of vitamin D? After all, if the level is reduced, then all the money spent, all the resorts are worthless. Not only that, lying in the sun under a thick layer of sunscreen, "free radicals" are formed on the skin, which can cause irreparable damage to health. Therefore, you should choose a sunscreen with physical rather than chemical filters. You should also "moderate" your solar appetite and a couple of days to devote to lying in the shade without sunscreen. Then do not run into the shower for at least one hour, so that vitamin D can be in the body.