Are all four of these forces ever in equilibrium? Does thrust ever equal drag and lift equal weight? Yes! Anytime the plane is not changing from one flight path to another, the forces are equal. That would be in straight and level flight, a steady climb or a steady descent, and when the speed is not changing.
In unaccelerated level flight, thrust equals drag and lift equals weight.
"Man cannot discover new oceans unless he has the courage to lose sight of the shore."
-- Andre Gide