[It was partly because of Mitsuba, but to claim that as the sole reason would be entirely dishonest. Her first thought on thinking she might be about to bleed to death wasn't quite that selfless.]
But-- [She shifts closer and exhales slowly.] I didn't want you to have to watch me die. [Maybe it sounds selfless. It wasn't. Lacus didn't want to see him in pain because she didn't think she could handle it. Guilt, plain and simple.]