so many things seem filled with the intent to be lost that their loss is no disaster. (1.2-3)
The implication here is that many things are destined to be lost, and even actively will their own loss; the speaker isn’t in control of what comes and goes in her life.
Lose something every day. Accept the fluster of lost door keys, the hour badly spent. (2.4-5)
This odd command suggests that loss is a permanent state of unsettledness, and that only by accepting its inevitability can we learn to cope with it.
Then practice losing farther, losing faster (3.7)
The expansion of this idea of the "art of losing" into the abstract begins in this line. The poem gains momentum as the poet loses things of greater and greater value, increasing our sense of instability and change.