Avos states, "Do not be as servants who are serving the master in order to receive a reward, rather be as servants who are serving the master not in order to receive a reward."

Yet, Mesillas Yesharim states:

The means that lead a person to this goal [i.e. World to Come] are the commandments which the blessed G-d commanded to us. The place of the performance of these commandments is only in this world. Therefore, man was first placed in this world so that through these means prepared for him here, he will be able to reach the place prepared for him, namely, the World to Come, there to be sated with the good which he acquired through these means. This is what our sages of blessed memory said "today to do them, and tomorrow to receive their reward" (Eruvin 22:1).

Then, he concludes:

The primary [purpose] of man's existence in this world is solely to fulfill the commandments, serve [G-d] and stand up to trials.

When my parents ask me to do something, I don't it to get something out of them. Rather, I do it because I have mitzvah to honor them - like what Avos advises. If I would do it according to Mesillas Yesharim, that would be either very egotistic or self-centered relationship.

How can we reconcile the passage in Avos with the Mesillas Yesharim's dictum?