Wasted life in Dockery and son

There is a quote by Helen Keller which states: “When one door of happiness closes, another opens; but often we look so long at the closed door that we do not see the one which has been opened for us.” I feel that this epitomises what Larkin was portraying in the poem 'Dockery and Son'; a feeling of regret and a wondering of what the 'other door' might hold. It could be seen that the older door of happiness is Larkin's youth: a time of freedom, when they could be 'unbreakfasted' and live without responsibilities; unlike the duties that Larkin portrays parents as having in Afternoons: "...an estateful of washing..." The fact that he is looking at this old door so long represents how others’ lives have progressed, such as Dockery, who has had a child; whilst Larkin has remained free and childish - an “unhindered moon…”
We see the reference to the doors themselves in Dockery and Son when he “...tried the door where [he] used to live/locked..." The enjambment here emphasises the fact that the door is inaccessible to Larkin, suggesting he realises that he cannot change his past. The metaphor of the train is used throughout; "I catch my train" to symbolise his life, and the track that he is on. The sound of train tracks is rather monotonous, suggesting that Larkin's own life is restricted by a routine which is the same as when he was a child and at school. (It is interesting that he is restricted by routine, something he always criticised parents for being.) The locked is also on a separate stanza to make it feel final ; as if Larkin has set a path for his life to follow till the end, there is a sense of finality in it. The reader can understand that Larkin has a moment where he regrets how little he has achieved when he refers to "The Lawn spreads dazzling wide..." The lawn perhaps is symbolic of lots of people, as if each blade of grass is a separate identity, and together they are resplendent (ie. he is stunned at the achievement of others. Achievements of blades