The speaker thinks (feels) that her daughter is growing up very fast and uncontrollably, so the speaker feels a wistful feeling towards past years in which her daughter was young and just learning to ride a bike, and the speaker wishes her daughter to remain forever in her chidlike state and never grow up.
The poet illustrates the speaker's feelings towards her daughter by drawing a comparison between different moments of their life. Both the moment when the speaker taught her daughter how to ride a bike and the moment when the daughter is leaving home are being compared. During her daughter's childhood, the speaker was by her daughter's side , yet she could not tell if she would have been able to prevent her daughter from falling off the bike . The poet says that the speaker waited for a thud while teaching her daughter to ride. The daughter finally got to learn how to ride and disappeared in the distance saying goodbye through her handkerchief. The daughter being a grown up now will leave home. Although the speaker must have done her best to take care of her daughter, she will never be able to prevent her daughter from suffering.
