得意淡然 (tokui-tanzen: not letting oneself get puffed up by success)
triumph (1st 2 chars.) + fleeting + sort of thing
Look at all the fire in the last two kanji! Fire (火) appears twice in its purest form in 淡, and 然 has the fire radical on the bottom.
We also see the water radical alongside all the fire in 淡. The presence of water would seem to explain how a double-dose of fire could be fleeting. But Henshall says that’s not the etymology at all.
So now you’re wondering what he did say. Fair question! He says that the double flame doesn’t actually refer to fire at all. Instead, it gives the sense of “plain,” yielding “plain water” or “water with nothing mixed in.” This doesn’t mean “pure water,” as one might think. Rather, it has come to mean “insipid and uninteresting,” with associated meanings of “light, faint, pale.”
Much more satisfying to think in terms of fire and water, somehow!