The sun might be "behind you" but the UV rays are all around you, sorry to say. I don't think there's anything inherently wrong about being in the sun or avoiding all sun, though. It's just a trade off!
Especially for me, I wound up having a serious vitamin D deficiency due to a combo of not getting sun plus thyroid issues and had to spend a couple of months on a mega-dose and now take smaller D supplements daily. I'm just glad my doctor diagnosed it, because I'm feeling a lot better now. I thought I could just get D from milk products, but that's a total fallacy - it's either the sun, a sun lamp or vitamins, and of course the real sun in the sky is best.
The extra precautions I take are for vanity too! That's ok by me.
I'll never have the porcelain white skin I had at 18 again. I look at pictures from back then and am pretty amazed - you don't always realize what you have when you have it. Sometimes I enjoy being out in the sun. It's so relaxing! At this point, I am just trying to keep things in balance so I hit the sweet spot between the health and fun benefits of nice sunny days and outdoor activities and keeping the age spots and so on at bay. Both have their good points.
When it comes to skin cancer, the number one most important thing is to keep aware of any changes you might be experiencing and get a semi-regular mole check from a dermatologist - often the most dangerous skin cancers are the ones you can't even see, because they're in some out of the way spot on your back, etc. Those can happen even with sunscreen and keeping covered up, so don't forget to get a decent check up ever so often!