There will always be times when writing is as appealing as scrubbing tiles in a public shower stall. But most of the time, it should be fun. And the joy with which you approach your work can help you make the most of the time you set aside to write. So, as you review your match of tasks and opportunities, add one element to your preparation -- motivation.
Punishments and rewards can work provide motivation (though the former isn't fun for most of us). While I know successful, old-school writers who are more stick than carrot, I don't recommend that route. One rough patch can make the whole idea of being a writer repellent. Who needs that?
Promises of treats, if the payoffs are gauged correctly, can kick-start activity. Just stay away from payoffs that can become unhealthy or addictive. Plenty of talented writers have been lost to alcoholism and drugs. Desserts can be a problem for some people. And I myself lost at least one novel to a video-gaming habit.
Nature and art offer lots of opportunities for positive rewards. So, instead of satisfying an appetite, consider buying a new plant for your garden or getting a massage or picking up a ticket to a concert.
Perhaps closer to a good way to motivate yourself is imagining achieving your goals. Classically, get rich quick books encourage readers to dream of piles of money. By analogy, you might envision yourself opening your newly published book or sitting in an audience, thrilled as the "written by" credit flashes across the screen in the theater. More modestly you can look forward to developing your characters to the point where they talk to you, or you can just recall the pleasant feeling of creating a well-turned phrase.
Rather than go the extrinsic route with negative/positive reinforcement, consider intrinsic choices.
The best of these is recognizing which processes you enjoy. Most people would put periods of composition when the muse takes over -- words pouring out that seem (at the moment) to be perfect -- at the top of their lists. I know writers who see editing a manuscript so the word total drops by thousands as a game that's challenging and engaging. I love interviewing my characters. The muse can't be summoned, only welcomed, but the other activities here are all ones that can be scheduled into your writing time. They can be guaranteed fun.
When you have good writing sessions, make a note to yourself. You may find that you can pepper your calendar with these activities or redirect yourself to them when you have dry spells.
In fact, it's not a bad idea to find a way to track your experiences. It can help you understand yourself as a writer. If you find that you have too many down days, in addition to scheduling in some fun, you can shake things up with something new. Most of the time, I write by typing or dictating, but about once a month, when I find those are uncomfortable (or a cause for dread), I shift to a notebook and a pencil. Usually, I get immediate relief.
The more you build good habits and include cues (like rituals) that tell your brain to get to work, the less you'll need to do something deliberate to bring the fun back. But having approaches ready when you feel restive or can't get to work can help you to get the most out of the time you open up for writing.