Wikipedia explains that superstring theory is an attempt to explain everything by modeling matter and forces as vibrations of infinitesimal strings. The strings vibrate at different frequencies and in harmonics with each other. For example, the graviton, which is responsible for gravity, is produced by a single string. This theory requires a minimum of ten different strings or dimensions to explain all the forces of nature, matter, and space-time.
Why is it that I want to type silly string instead of superstring? But I digress. LHC experiments put supersymmetric theory on the spot explains that researchers at the Large Hadron Collider are not observing what superstring theory predicts. Specifically, B-mesons are not decaying as fast as they should. Also, two other experiments at the collider have failed to detect supersymmetric particles, prompting the BBC article to say, supersymmetry has 'bit the dust'.
This declaration is discouraging physicists who have come to believe the theory is beautiful and explains everything.
But the beauty of science is that you propose a theory and then begin to either prove or disprove it. If your theory is incorrect, then you get to invent a new theory - sort of like perpetual job creation. Seriously though, the older physicists are discouraged the theory they have come to love isn't working out, while younger physicists are excited at the opportunity to invent the true explanation of how everything works.