"For he was not old; his life was not over; not by any means. He was only just past fifty." (pg. 43)
Aging is an important part of Mrs. Dalloway. All of the characters are feeling the effects of growing older and older-- Clarissa has recently been ill and is concerned about how old she looks; Peter is now fifty and feels somewhat like he has accomplished nothing in his life, etc. Many of the characters spend a great deal of time looking back on their past and wondering if they made the right choices. Clarissa goes back and forth throughout the entire book about whether she made the right choice in not marrying Peter as a young girl. Even though she asserts that she is happy in her life (much like Peter does), both Clarissa and Peter fear their aging and wish to be young again.