A failure or so, in itself, would not matter, if it did not incur a loss of self-esteem and of self-confidence. But just as nothing succeeds like success, so nothing fails like failure. Most people who are ruined are ruined by attempting too much. Therefore, in setting out on the immense enterprise of living fully and comfortably within the narrow limits of twenty-four hours a day, let us avoid at any cost the risk of an early failure. I will not agree that, in this business at any rate, a glorious failure is better than a petty success. I am all for the petty success. A glorious failure leads to nothing; a petty success may lead to a success that is not petty.

-Arnold Bennett, How to Live on 24 Hours a Day

The notion that "If you fail at this you will fail at this forever" is very dangerous to depressed people,

A dangerous truth is still true. Let's not recommend people try at things if a failure will cause a failure cascade!

TDT doesn't say anything useful [...] about entities that change over time

The notion of "change over time" is deeply irrelevant to TDT, hence its name.