Just chewed out for giving my resignation, how do make through the 4 week notice period ?

So I work for a small company two people who report to a board…we are understaffed. I gave my notice cause I got a 20% raise someplace else and my boss was pissed because we have a big project coming up and the timing is bad and then called me out for taking leave for my new baby. Gosh, they didn't need to be happy about it but some tact would be nice.