Flaca

This song seems to be about a love affair that ended.

I'm not sure though if the guy is now trying to resist the pain of it (as suggested by the song mood and implicit meaning), or to stop the girl from emotionally blackmailing him, claiming that he was never emotionally attainable anyway (as suggested by the façade of the lyrics and the explicit meaning).

The guy asks the girl ("flaca" is slang for girl in Argentina) not to stick her knives into his back, claiming it doesn't hurt him at all. Then he says that far in the center of the earth, the roots of love stay where they are. The use of "far" and "stay" seem to suggest that he claims he wasn't affected by the "love affair". The roots didn't grow... On the other hand, this can also be interpreted as if the roots are solid, strong and eternal, and they don't break.

The girl left him some "lost Aprils" in the closet of the "guest room". This can either refer to memories or pieces of clothes that stir memories. These were the "golden times" of a better past. There seems to be acknowledgment that the love affair had some good moments, but that since then it took a turn for the worst. The use of the "guest room" suggest that he never let her in to his inner rooms, so he's not vulnerable to her.

Even though he was almost wrong and told her sometimes "don't lie to me", "don't tell me the truth" etc. - these are words that people who care use against their partner. These are emotional words said in response to hard emotions. This implies that he is saying now that he almost cared in the past, but only almost...

Even though he almost confessed that he was a bastard (dog) of a partner - then he breaks the thought and says: an ideal dog, that learned to bark (as some lyrics use ladrar) or swim (nadar) and to return home to get food. So it starts as if he was the bad one, but then it switches that he was like a dog, who had to depend on the love (food) of his woman.

The image here for me is someone trying really hard to feel strong again, and pretend that there was never a strong love, and that he was not as dependent as he seems to really have been.