If you choose to ' keep ' a guyKeep in mind forever. .. It must be accepted.Both feel painful and beautiful.It is time to ' think different. 'Because of that we keep him in mind.It shows that the"He is already with us."
If you choose to 'keep' someone in mind forever. .. I have to admit , the feeling of pain and beauty that it hid together. 'Time to think up' because we choose to keep him in mind , indicates that "he is not with us."