For myself, I have two main creative outlets that take up most of my personal free time, and I alternate between the two depending on how I feel. I find them both rewarding and never regret the time spent on either - even when I don't produce anything of any value. I understand going in that there will be fruitless sessions (in terms of quantifiable output), so I count them as a price to get to the stuff of value, which is subjective anyway.