So next time you need to resist temptation, improve your mood! Smile or laugh, watch a funny video or two.

no. This is reaching not-even-wrong territory.

On what basis? It matches my experience, something similar has been discussed on LW before, and it would seem to match various theoretical considerations about human psychology.

Truth is - if there were any ideas that really worked; you would already know about them; and probably already be using them.

This seems like a very strong and mostly unjustified claim.

E.g. even something like the Getting Things Done system, which works very well for lots and lots of people and has been covered and promoted in numerous places, is still something that's relatively unknown outside the kinds of circles where people are interested in this kind of thing. A lot of people in the industrialized world could benefit from it, but most haven't even tried it.

Ideas spread slowly, and often at a rate that's only weakly correlated with their usefulness.