Please see Ber. 44:31. Isn’t the word vehaya supposed to mean something good (Ohr Hachaim to Devarim 11:13 quoting Midrash)? How can that apply here?
This is a very good question. The sefer Likutei Yehudah brings from the Imrei Emes who asks this question, and he answers that since it says it because we have to be happy and bless H-ashme for the good just like the bed, it was possible for Yackov to still be B’simcha even in such a hard situation. So why would he die from it? He says that although intellectually he could do it, however his physical body wouldn’t be able to handle it, similar to when Sara died when hearing about the akeida.
The sefer Lechem Haponim- 4 (R’ N. Dayan) takes a different approach. He says that V’ haya only mans good when it says “V’haya bayom”, but when it is alone, it sometimes mean good and sometimes bad. This is similar to what it says, that “V’yehi” sometimes means good and sometimes bad, but V’yehi B’ymei” always means bad.