It's easy to find out that the poem is talking about "Losing" from the repeating sentence "The art of losing isn't hard to master". What is the poem trying to express? How does the speaker feel? Does she really think it the way she had said in the poem?
"The art of losing isn't hard to master; so many things seem filled with the intent to be lost that their loss is no disaster." Losing, this thing is something what you can't prevent. It will happen anytime, anywhere. You can't help losing things. Even if you try your best to keep it by your side, it will still get legs and run away while you're deep at sleep at night. You see, "so many things seem filled with the intent to be lost", things themselves have the desire to get lost. There's no use forcing them to stay. This is a principle; you have to follow it. It's natural; something that you can't stop can't change. Therefore, the loss is no disaster. That's how things go.
"Lose something every day. Accept the fluster of lost door keys, the hour badly spent. The art of losing isn't hard to master." This stanza is kind of teaching us to lose. The note of the speaker is like a teacher. When you go on to the next stanza you can find the word "practice", it feels like the speaker is kind of enticing us to lose things. You have to learn it, get use to it, and accept it. How do you feel when you lose your keys? Panic? Flustered? Worried? But can you get your keys back by all these emotion? Is there any help by walking backward and forward and having this miserable look in your face? The thing that you can only do is wait for an hour or two, and somebody will come home and unlock the door. Or you can get the help of the locksmith. It really isn't a big deal. Spending the hour badly, is just a waste of time. The hour has already past away, don't stand there mourning over it. So what!? It's only an hour, move on, you still have plenty of hours. And at the end of the stanza it repeats again-The art of losing isn't hard to master.
"Then practice losing farther, losing faster; places, and names, and where it was you meant to travel. None of these will bring disaster." What the speaker mentioned in the front stanza, really are just small, tiny things. They don't hurt that much. Now, she is telling us to lose things bigger, and lose them faster. During the journey of the life, we don't just lose things like keys or time; we lose things like opportunities going to places we dreamed for, meeting people, etc. In spite of this, it's not the end of the world. So, there it goes again: None of these will bring disaster.
"I lost my mother's watch. And look! My last, or next-to-last, of three loved houses went. The art of losing isn't hard to master." I think "my mother's watch" must be something precious, something more expensive. Or maybe watch suggests time. And by putting them together, it means that she lost the time gathering with her mother. Another possibility is that her mother has already past away. And what about "Houses"? We know house is a refuge, and refuge suggests close friends or relatives. Whenever we have tough times, we might go to our close friends, share our sorrow, get warmth from them and feel better. It will make us feel better. So, she lost three close friends of her. But maybe, I'm thinking it too complicated. Maybe the speaker just lost three houses. Anyhow, we can still get through of this kind of loss.
"I lost two cities, lovely ones. And, vaster, some realms I owned, two rivers, a continent. I miss them, but it wasn't a disaster." Now, what does cities, rivers, and a continent mean? Am I thinking it too complicated again? We know that cities and rivers are included in a continent. So I was thinking, maybe this is talking about her business. Cities are small cases; she had difficulties on her job and lost two cases. And then, her business became worse and worse, so she lost rivers. Finally, she failed in her work, and lost the whole continent.
"-Even losing you (the joking voice, a gesture I love) I shan't have lied. It's evident the art of losing's not too hard to master though it may look like (Write it!) like disaster." "You" here, I think this must be the speaker's lover. And there seems to be a big change in this stanza. She changed her note. She said that loss was not at all a disaster in the previous stanzas, now she said it is like a disaster. Why does the poem present these two words "Write it"? This is because she is painful about these losses; she does care about them. She was kind of escaping from the truth, and telling herself its nothing at all. Though, it indeed is a disaster.
The main idea of the poem is that we should treasure what we own now. When we lose it, just let it go. Don't feel sorrow or pity, that's how life goes. Remember that we were given birth and entered into this world with nothing. We don't have the right to keep all the things we have now forever. Just appreciate them the time when you have them.