One should add an additional light each night (of Chanukah) (Orach Chaim 671:2).
Although frequently translated as "dedication," Chanukah also means "renewal." The way that we celebrate Chanukah teaches us that renewal requires something more than returning to a former state, even if that state itself had been satisfactory. Renewal requires advancing beyond the previous state.
I once heard a recovered alcoholic, twenty years sober, say, "The man that I was drank, and the man that I was will drink again." If people who emerge from a deteriorated state go back to the state prior to the deterioration, nothing has been accomplished, because history will repeat itself. To avoid the deterioration from recurring, they must change themselves into new beings.
To achieve a renewal, we must progress. Adding a Chanukah candle every night symbolizes this concept in a spiritual way.
Remaining at a plateau is hardly desirable for anyone, but it is utterly unacceptable for people who seek renewal. For them, progress is not only essential for growth, but for survival.