As a career artist, one thing I hear a lot from friends who are exploring creativity is "I'd love to come over and have an art day with you." When art is your job, every day is an art day. I always think it is funny because I never hear anyone say to my sister "I'd love to comer over and have a day of writing closing arguments with you!"
Art-a-day challenges are very popular on social media, mostly for the creator of the challenge who requests you tag their challenge name in every piece you create and post. Art-a-day challenges are great at driving traffic to other people if your challenge is really about them and not you. I am a huge believer in personal projects. Art projects you create because the desire to do a certain project or learn a new medium won't let you go. A personal project is all about what YOU want to create. No client is involved, no person you have to tag, no sales to worry about, no social media group creating the exact same thing you are. You are creating for you and only you. Creating for yourself because the idea you have is keeping you up at night matters so much, especially when you create for others every day. Personal projects are usually where you learn the most, have no fear of failure, there's no expectation, and the main thing driving you is your passion to create. You are the boss of your personal project. Absolutely nothing has to come from your personal project. Though, it usually happens that personal projects have a way of turning into work projects once you see them through...and that is the magic of them!