@dinofelis: Yes, you're right - I have clarified it in an edit of my post but you were faster
The point is that, as you say, you can only receive Bitcoins from the node with whom you have a open channel (let's call it Alice). But another user (let's call him Bob) that has a channel open with Alice can do payments to you using Alice's node. What really happens is that Bob moves coins to Alice and Alice to you. That would be the way to "reload" a channel.
Ok, that's more or less how I understood it. But the tricky part is that, with relatively small amounts in channels, you have to be at "average wind still places" for them to be able to function a certain time before being "pushed against a wall".
None of your channels can be on a "systematic flow" from one place to another. If you are, your channels will quickly be "exhausted" in the meaningful direction, at which point you have to settle and reload them (ok, you can wait for the occasional transaction in the other direction, true).
Suppose, in our example, that Joe regularly receives payments in bitcoin, and has his favorite bitcoin store at Bob's, who is a bitcoin-accepting merchant. This means that Alice will regularly see payments that go from Joe to Bob. Very rarely, Bob pays Joe in bitcoin, which would be the way to relieve Alice's exhausted channels (in one direction).
In fact, in the given situation, when Joe has done 2 payments, Alice's channels are exhausted: Joe/Alice is at 0 / 2 and Alice/Bob is at 0 / 2.
Now, Alice can wait for the occasional transaction that Bob does to Joe. But most of the time, where she is, these payments go in the other direction. So the best Alice can do, is to settle, and start again a channel with 1 / 1 with Joe, and 1 / 1 with Bob. To be exhausted again after 2 payments.
In this particular case, it makes absolutely no sense for Alice to use the LN: she does more on-chain settlements than transmitting LN transactions !
Suppose now, that Joe is rich. He has 100 BTC which he might spend at Bob's. But Alice isn't rich. She's just operating her LN node.
Joe could open an asymmetric channel to Alice: 100/1. But Alice cannot open an asymmetric channel to Bob. She has only one BTC left.
So she opens a 1 / 1 channel with Bob.
Joe pays two times 0.5 BTC to Bob through Alice. Joe/Alice is now at 99 / 2 ; but Alice/Bob is at 0/2. And Joe cannot send another transaction to Bob through Alice without Alice settling first with both guys, take the 2 BTC from the Joe/Alice channel, and start over:
99/1 and 1/1 respectively.
Suppose on the other hand that Alice is also rich. No problem this time:
Joe opens an 100/5 channel with Alice, and Alice opens an 100/1 channel with Bob (she knows that Bob only receives coins, and rarely spends them, but she wants some engagement from him).
This time, Joe can do 200 LN transactions through Alice towards Bob, before they are in 0/105 and 0 / 101, and need to settle.
200 transactions for 2 settlements, that's fine.
This example is, I admit, extreme. But it shows how "being a rich node" increases dramatically the efficiency of using an LN node.
