Life is what happens to you while you're busy making other plans

I hate when certain scenarios make a normal everyday thing and make it sad. Especially when the thing would never have sad thoughts without that scenario.

Case in point: I was listening to my iTunes and "Beautiful Boy (Darling Boy)" by John Lennon popped up on shuffle. It is such a nice song written by a father for his son. Until I heard this line that made me sad:

"I can hardly wait
To see you come of age
But I guess we'll both just have to be patient
'Cause it's a long way to go
A hard row to hoe
Yes it's a long way to go
But in the meantime
Before you cross the street
Take my hand
Life is what happens to you
While you're busy making other plans"

I had never paid attention to the first part of that stanza, but good lord if this doesn't sound haunting and sad. He would not see his son come of age. He was busy making plans of raising his son when life decided to step in the way. I wonder if his son can listen to this song now without feeling depressed.