Is fasting one day and breaking fast the next, along with observing vigil in the last third of the night, considered extremism in religion?

Al-Bukhari and Muslim narrated that the Prophet, peace and blessings be upon him, said: "The most beloved prayer to Allah is the prayer of David, peace be upon him, and the most beloved fasting to Allah is the fasting of David. He used to sleep half the night, stand in prayer for a third of it, and sleep for a sixth of it, and he used to fast one day and break his fast one day." This fasting and that prayer are the best deeds, and it is not extremism but rather hastening to good deeds. However, one must accustom oneself gradually, for a little that is continuous is better than a lot that is interrupted.