Some days will be bad. Friction and uncertainty are implied when trying to create something, and that means not all plans will work out.
But the default day can be designed to lean towards good. Break projects into smaller pieces, make a lunch walk a habit, sneak some reading into the day. Find what gives you a boost and design your day so that it incorporates these nuggets.
Nobody owes you a good day, but if we’re spending it sitting in front of a screen with air conditioning and a water fountain close by — we still have it better than almost everyone in the history of humanity.