It takes time, many rejections, and some common sense to shrug off rejections. Non-responses hurt more, because they leave an element of doubt.
For whatever reason, that particular agent at that moment didn't respond to your query. Or they had a partial, and couldn't fall in love with it. Or they had a full and couldn't sell it. And rather than tell you, they dropped you. Life goes on. There are other projects to try. The important thing is to realize when something is becoming a personal brick wall that you cannot breach...yet.
I've been lucky. Some experiences in the art world taught me when to back off. I would love to have my art represented by a certain gallery in New Mexico; it's one of the top five in the U.S. for my type of art, they do great business even in a recession, and being with them opens serious doors for an artist. I've been trying for ten years. I'm closer now than I ever have been, but it required focusing on other credentials that might prove I'm a good business risk. I have never whined at or argued with the gallery owner, in my several attempts to jury in. She'll either thaw, or I'll find another gallery in the same area that will love my work.
Not long ago, a husband and wife art team began a critical art blog in my hometown. Some of their postings were hilarious, spot-on, and deeply philosophical. Because they didn't pull their punches, they made enemies. Over six years, the blog's tone devolved into incoherent and paranoid rants about specific local artists and galleries that were 'dragging them down and shutting them out'. The economy soured, the writers vanished, and their blog is only a placeholder now.
The really sad thing is that my hometown would be a terrible market for their art and writing. They had a magical-realism graphic novel that was amazing. I and several other artists gave them names of other galleries in other states, along with publishers, but these two were so driven by one unrealistic goal that they've probably lost everything.
Choose your battles.