Glorifying Hashem:
Rav Avrohom Chaim of Mikoliov zy”a, a son-in-law of Rav Meir of Premishlan zy”a, explains that the word “neder” can also connote “hiddur”, glorifying. Accordingly, he explains the words “ish ki yadur neder l’Hashem oh hishava shavua la’asur issur al nafsho” to mean that if a man wants to glorify something, he should praise Hashem (l’Hashem”). But if he speaks about bad things (the word “la’asur issur” can mean to speak “sarah”, negatively), then he should speak “al atzmo” (about himself).
We can learn from this that one should give credit for his successes to Hashem, while taking the blame for his failures upon himself. When one succeeds in any matter, he should praise Hashem and thank him for granting him success. When one fails to succeed, he should not blame it on Hashem. Rather, he should realize that he is to blame.
