You seem to be taking it as a given that failure reflects on you. This represents a tremendous toll on mental energy, and it's the very first type of belief that I train people to get rid of in order to stop procrastinating and increase their throughput.

If you're worried about whether something is an excuse for failure, in other words, you're already thinking too much about failure for your own good.

See Seligman (optimist/pessimist thinking) and Dweck (fixed/growth mindsets) for why... in particular, note that their experimentally validated models of successful and struggling people's thought processes blow away your model of what "extenuating circumstances" to consider.

Optimists and "Growth"-minded individuals have no problem using extenuating circumstances to explain the past, since the past is already over and not subject to modification. Their focus is on what they learned about what they should do in the future. But this isn't "excusing" anything, because they're not under the mistaken impression that failure actually reflects on them.

When I consider doing less, I consider that this would make me a horrible awful unforgivable person. And then I cheerfully shake hands with others who aren't trying at all to save the world.

This is pretty much a standard thought pattern that crops up in treating people with the "fixed" mindset; you can find plenty of examples in the dialogues of Robert Fritz's books, where he uses logic to debunk the idea that a person needs to justify their existence by saving the world... or doing anything worthwhile at all. I used similar methods to get rid of my compulsions along those lines.

Note that it is entirely possible to want to save the world because it makes you feel good, not because the lack of that effort will make you a terrible awful person. I still have my own world-saving mission, though I went through a rather confusing period where I still associated that ideal with the negative compulsions that previously drove it. Took a while to realize I could have the positives of the mission, without needing to make it "serious" in the self-righteous way that I did before.