You could have come up with the best excuse for why your book did not get published when you said it would. The best excuse does not change the result–the book was still not published at the time you said it would be published.
“I didn’t study for the test because I had a project that week.” Although this excuse was well done, it does not change the fact that the person scored a low grade on the test.
“I don’t use Instagram because I don’t want to start from scratch when I have 500,000 followers on Twitter.” This is not an excuse. This is a logical reason. Focusing on the 500,000 followers on Twitter is more important than creating the Instagram account.
There is a difference between a reason and an excuse. An excuse is a cover up for a flaw on your part that could have been addressed better. It is better to admit mistakes than to cover them up so everyone can learn from those mistakes, not just you. A reason is something that makes sense but is not trying to cover up a flaw. Not having an Instagram account is not a flaw when you have a strong presence on Twitter. Likewise, not having a Twitter account is not a flaw when you have a strong presence on Instagram.
Excuses should not be tolerated. Mistakes should be admitted. Excuses are just the long route that ends up going exactly where the short route goes–the realization that there is a flaw. Reasons are good especially when they can be supported. Reasons are logical, and reasons don’t hide flaws because there is nothing to hide.