The ADHD brain is motivated by interest and urgency, not importance. Not just a cognitive interest, but an emotional full-being type of interest.
While you thought through the writing project very carefully, cognitively, you may not have considered if you’d have the excitement and emotional connection you need to stick to it and not quickly lose interest.
It also sounds to me like you beat yourself up a lot, evidenced by your second comment that you were frustrated with yourself for writing this post instead of doing something else. Practicing some self-compassion could help a great bit. Go easy on yourself. Know that you won’t always be passionately connected to all tasks you do, but that doesn’t mean they aren’t worthy tasks, and it doesn’t mean you’re somehow a bad person or making mistakes.
ADDitude Community Moderator, Author & Trainer on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism