Rashi says that “Avoda of the heart” means Tefila, and he brings a proof from Dovid who said: ת כוֹן תְפ לָת י קְ טֹרֶּת לְפָנֶּיךָ תהלים קמא ב my Tefila should be pleasing to You just like the Ketores, which is an Avoda in the Bais Hamikdash. Why did Dovid choose Ketores; there are so many other kinds of Avoda in the Bais Hamikdash?
We can suggest that Dovid picked the sweetest and most Geshmaka Avoda (which also makes you rich) since Dovid was full of sweetness, as he was called: נְע ים זְמ רוֹת י שְרָא ל ש"ב כג א the sweet singer of Israel. A person should learn from Dovid to try to make his Tefilos Geshmak and sweet. There was a Chasidishe Rebbe who had a band playing music while he davened!
Look how Dovid always looks to make his Avodas Hashem full of Simcha and pleasantness every time. When he danced, he also got carried away, and his wife Michal felt that it was even too much. This was Dovid’s greatness, and this is why he is our Melech who teaches us to always try to make our Avodas Hashem Geshmak.
All the Korbanos are called: ר יחַ נ יחוֹחַ לַה' an appeasing fragrance to Hashem, even though they didn’t smell that good (and sometimes they smelled bad
