  In magnetic systems with dominating easy-plane anisotropy the magnetization
can be described by an effective one dimensional equation for the in-plane
angle. Re-deriving this equation in the presence of spin-transfer torques, we
obtain a description that allows for a more intuitive understanding of
spintronic devices' operation and can serve as a tool for finding new dynamic
regimes. A surprising prediction is obtained for a planar ``spin-flip
transistor'': an unstable equilibrium point can be stabilized by a current
induced torque that further repels the system from that point. Stabilization by
repulsion happens due to the presence of dissipative environment and requires a
Gilbert damping constant that is large enough to ensure overdamped dynamics at
zero current.
