The only rejections I’ve ever had have been from the big national conferences to which I’ve submitted my work, and the rejection is double-edged. On the one hand, you can take some comfort in knowing that your abstract was one of many that were rejected and that this is just the way of the large competitive conference (and when the breakdown of what abstracts were submitted and which were accepted comes out, you can pour over the stats and make wise pronouncements on the subject). On the other hand, you have to live with the fact that apparently the program committee at your national conference thinks the work you do isn’t significant enough for that platform, and that your work won’t be showcased in front of that large audience of your peers. I have to say that after going through the rejection process for these large conferences several times, I’m just viewing the whole experience as based entirely on luck and whether there were enough complementary abstracts to make up a panel.