The speaker says that this sweet talk (heat of speech) is because he has kept a candle lit from dusk till dawn for a lifetime. (The candle represents continuous effort or effort over a long period).

This beautiful couplet speaks of endurance and sustained passion. The poet says he spoke about the 'heat of his words' (garm-e-sukhan), implying that the effort of speaking itself was exhausting. But the depth of the line lies in the simile: keeping a candle lit from dusk till dawn. It signifies a continuous, unwavering devotion or struggle that lasts through the darkest, longest night.