Colouring books. They're getting ore and more popular as I type. They're stress-relieving, meditative and calming for adults. If you feel stressed out, you can pick up colouring pencils, pick a page of your book and relax by colouring. You can add more detail with pen, colour what's in the picture and lots more-whatever you want to do.
I personally like to take an extra step further by drawing my own pictures in my art journals. Then I colour how I want/add more detail. Everyone's different and unique-some have a reason to pick certain colours and others pick randomly. Whatever works best for you is fine. Whether you choose colouring books or art journals, both require creativity. You need to colour the image-either hand-drawn or printed-and get creative with your choices