@Shelley-James-0 I work as a teacher, too, albeit in higher education. And I know how it's more work than a simple 9-to-5 sometimes. My position as my theatre department's costume designer means that many evenings are eaten up attending rehearsals on top of classes taught during the day, and the days can be quite long... It's hard to find the motivation and the drive to get work done.
I think the trick might be to find a "low time-investment" drawing activity that doesn't require large chunks of time set aside to accomplish. That way you will feel a sense of accomplishment without having to also feel too busy to do anything.
For example, I watched a video of an oil painter today that has suggested painting small 6x8 still life objects (like a piece of fruit or a vase) in 30 strokes or less. It helps you imagine the plains and shapes of various tones in the object, work with thick paint, choose colors before they mix on the canvas, work with larger brushes, and make purposeful strokes. 30 of them. That's all ya got.
I wonder if something like that might be useful for you? Or create partitions in your work by only working on parts of each drawing, or only accomplishing one step in the drawing for the chunk of time you've got. The challenge is to develop an approach that can be "compartmentalized" into steps and portions that you can recognize, articulate, separate on purpose, and then feel good about accomplishing each part instead of a complete work.
I, too, have had problems completing monthly challenges, for example, and there are simply some months I haven't participated at all. I haven't done any of them since December, and my time to be present on these forums has decreased considerably. My attention has been purposely elsewhere. For good reasons.
And you have to be okay with that. It is easy to get buried under the mountain of learning and practice you have to do to become competent in the illustration field, but that's no different than the slew of education courses you had to take to become qualified as a teacher (and have to continue to take each summer...) Remember you can't compare your progress to another's pace because there is no formal structure like attending an actual school and being in an actual class provides.
Break up that 1.5 hours into 15- or 20-minute increments so you are purposely making smaller illustrations and feel a stronger level of accomplishment and progression. Put the pressure to participate in. its. place. and instead celebrate the smaller milestones in front of you. At a certain point, I had to realize my development as an illustrator was better spent investing my time in things other than challenges. I suspect you might be in the same boat.
! I'm by nature not a routine guy at all, so I really need to schedule to make schedules with alerts built in. I use the BeFocusedPro app, and I have it set it so that I work in 50 minute chunks of time. So when I start doing my graphic design work, I hit start on the timer, and after 50 minutes, an alarm sounds, and the screen switches to a 10 minute timer for a break. Once the ten minutes is done (while I'm drawing), I start a new 50 minute block of work.