  A generic mechanism of collapse in the Gross-Pitaevskii equation with
attractive interparticle interactions is gained by reformulating this equation
as Newton's equation of motion for a system of particles with a constraint.
'Quantum pressure' effects give rise to formation of a potential barrier around
the emerging singularity, which prevents a fraction of the particles from
falling into the singularity. For reasonable initial widths of the condensate,
the fraction of collapsing particles, which are thereby removed from the
condensate, is found to be a 'universal' number $\simeq 0.7$.
