quiets himself. Hamlet also realizes that his inner thoughts are disturbing and forces himself to stop thinking about suicide when Ophelia enters the scene. He needs to prepare himself to act in front of Ophelia which is why it is necessary for him to stop speaking about his true feelings. 

Hamlet has been speaking his famous soliloquy which begins with "To be, or not to be: that is the question." He is, of course, speaking aloud, although he is expressing his own thoughts to himself. When he says, "Soft you now," he is telling himself to stop soliloquizing, probably because his soliloquy contains such morbid thoughts, including thoughts of suicide. He has to put on a different face and a different manner with this delicate young woman. Evidently she is holding a prayer book, and he seems to be asking her to remember him in her prayers (orisons). Some critics believe that he is referrring to sins they have committed together when he says, ". . . Be all my sins remembered." In other words, if she is praying for forgiveness for her own sins, they would automatically include Hamlet's sins if they had been involved in a carnal relationship. This seems like a remote possibility, although much later when she has lost her mind, she recites a suggestive verse, beginning with "To-morrow is Saint Valentine's day" and ending as follows:

Quoth she, "before you tumbled me,
You promised me to wed."
He answers:
"So would I ha' done, by yonder sun,
An thou hadst not come to my bed."  (4:3)