I didn’t know the full dimensions of forever, but I knew it was longer than waiting for Christmas to come.

The line frames “forever” not as an abstract metaphysical idea but as something a child can measure emotionally: the agonizing stretch of time before Christmas. By admitting he doesn’t grasp the “full dimensions” of eternity, the speaker underscores human limits—yet he still possesses a practical, felt knowledge of duration. The comparison blends innocence and melancholy: childhood anticipation becomes a yardstick for the unbearable length of waiting, suggesting that longing and deferred desire can make time feel infinite. In Brautigan’s typical mode, the plainspoken, whimsical image carries an undertow of loneliness and existential unease.