[46b top] R’ Nosson: Making a Neder (vow) is like building a Bamah (an unauthorized altar for sacrifices).
[Nedarim 22] Ran: The two are compared because in both cases people think they are doing Mitzvos [ie: “G-d should love this because I am bringing Him sacrifices! or “Hashem loves when I make extra “Holy” rules and regulations!”].
Chofetz Chaim: The Yetzer Hara many times dresses up Aveiros to look like Mitzvos.
D-E-ep Thoughts: Whenever we are “extra-excited” to do Mitzvos we should double-check our ‘Yetzer Hara guide.’ Are we really so enthused because we enjoy working hard and being selfless to come closer to Hashem, or are we secretly being driven by false evil drives for fortune/fame? May we all do good deeds truly for the sake of Heaven and only do what G-d truly wants us to.