Parsha Toldot - Chapter 25 - Verse 22
Halacha of Modei Ani and Al Netilat yadaiyim
Esav and Yaakov were running and pushing to get out and what she could not understand, one running inside her for Torah and one running inside her for Idol worship. Rivka was so upset, she couldn't understand a child wanting both, she did not know that she had two children inside of her. The pain of her pregnancy was so great that she said, "why me!", "why did I daven for 20 years for this?"
The Midrash says, that the 12 tribes were all supposed to come from Rivka, but she lost it all because she complained and therefore, never had any more children. Our lesson, Never complain. What we think is terrible, is good from Hashem. Never be upset about a situation that Hashem puts us in.