  Measurement combined with feedback that aims to restore a presumed
pre-measurement quantum state will yield this state after a few
measurement-feedback cycles even if the actual state of the system initially
had no resemblance to the presumed state. Here we introduce this mechanism of
{\it self-fulfilling prophecy} and show that it can be used to prepare
finite-dimensional quantum systems in target states or target dynamics. Using
two-level systems as an example we demonstrate that self-fulfilling prophecy
protects the system against noise and tolerates imprecision of feedback up to
the level of the measurement strength. By means of unsharp measurements the
system can be driven deterministically into arbitrary, smooth quantum
trajectories.
