As with everything, I guess do it in moderation and don't be stupid...?

Planning on being out a full day under the summer sun as a very pale north European? Slob on all the sunscreen that you can and hide in the shade when possible.

A day out in mid September / mid March when the sun is not looking to murder you? Revel in it. Soak it up. Be a plant.

Also it makes a lot of difference where you are. Scandinavians rarely wear sunscreen but their UV index is much lower than, say, California, let alone Australia.

Also, critically, get regular sun exposure so that your skin adapts. Ideally do this before it gets intense.