" The negative consequences if I turn out to be wrong seem insignificant - oh no, I tried to deceive myself about my ability to feel differently than I do!"

Repression anyone? I think directly telling yourself, "I don't feel that way, I feel this way!" can be extremely harmful, since you are ignoring important information in the original feeling. You are likely to express your original feelings in some less direct, more destructive, and of course less rational way if you do this. A stereotypical example is that of a man deciding that he should not feel angry that he did not get a promotion at work and then blowing up at his wife for not doing the dishes properly. Maybe there is nothing to actually be angry about, and screaming at his boss certainly wouldn't accomplish anything, but ignoring the feeling as invalid is almost certain to end badly.

I think Alicorn is suggesting that if you attempt to understand why you have the feelings you do, and if these reasons don't make sense, your feelings will likely change naturally without the need to artificially apply different ones.