Without Simcha One Can Forget Hashem

Sefer Mesilas Gad quotes Rav Gad’l Eisner zt”l as saying that since the word “v’haya“ always means simcha, the pasuk can be translated to be saying: “V’haya im shachoach...” If one forgets “v’haya”, meaning that he forgets to be happy. “Tishkach es Hashem Elokecha.” He will come to forget Hashem.