Mordin knew there will always be trouble lurking, either for him or for Shepard. He tried to ignore that such thing was round the corner, after all he couldn't trouble himself with such thoughts, he had a mission to do, and he will see it to the end, even if the cost was his life. Every time he saw Shepard, he knew that he can never look at the troubles that might come, because they could do anything, after all they had proved it by going through the Omega 4 Relay and destroying the Collector base. He could do it.