What are the implications of "ha'Yashar ve'ha'Tov"?
Rashi #2 (in Re'eh, 12:28): "What is right" - in the eyes of man and "What is good" in the Eyes of Hashem. 4
Ramban: To figure out what is right and good in the Eyes of Hashem 5 and to do it.
See R. Chavel's footnotes on the Ramban.
Ramban: The Torah inserts this after the command to observe the Mitzvos that are obligatory, to teach us to do what is right and good even regarding matters that the Torah did not command us. See Ramban, DH 've'Zeh Inyan Gadol', who elaborates. Refer also to 12:28:2:1.
By sometimes foregoing one's rights. See Torah Temimah, notes 72 & 73. Bava Metzi'a (108a): Due to this, if one transgressed the law of Bar Metzra (he bought a field that the owner of the neighboring field would have wanted to buy), the latter may take it from him [for the price he paid].
See Sifsei Chachamim there.
And not necessarily what is right and good in one's own eyes.
What are the connotations of "Lema'an Yitav lach"?