I'm doing pathfinding where I use force to push body to waypoints. However, once they get close enough to the waypoint, I want to cancel out the force. How can I do this? Do I need to maintain separately all the forces I've applied to the body in question?

I'm using Box2dx (C#/XNA).

Here is my attempt, but it doesn't work at all:

   internal PathProgressionStatus MoveAlongPath(PositionUpdater posUpdater)
    {
        Vector2 nextGoal = posUpdater.Goals.Peek();
        Vector2 currPos = posUpdater.Model.Body.Position;
        float distanceToNextGoal = Vector2.Distance(currPos, nextGoal);
        bool isAtGoal = distanceToNextGoal < PROXIMITY_THRESHOLD;

        Vector2 forceToApply = new Vector2();
        double angleToGoal = Math.Atan2(nextGoal.Y - currPos.Y, nextGoal.X - currPos.X);
        forceToApply.X = (float)Math.Cos(angleToGoal) * posUpdater.Speed;
        forceToApply.Y = (float)Math.Sin(angleToGoal) * posUpdater.Speed;

        float rotation = (float)(angleToGoal + Math.PI / 2);

        posUpdater.Model.Body.Rotation = rotation;

        if (!isAtGoal)
        {
            posUpdater.Model.Body.ApplyForce(forceToApply, posUpdater.Model.Body.Position);
            posUpdater.forcedTowardsGoal = true;
        }

        if (isAtGoal)
        {
            // how can the body be stopped?

            posUpdater.forcedTowardsGoal = false;
            //posUpdater.Model.Body.SetLinearVelocity(new Vector2(0, 0));
            //posUpdater.Model.Body.ApplyForce(-forceToApply, posUpdater.Model.Body.GetPosition());
            posUpdater.Goals.Dequeue();

            if (posUpdater.Goals.Count == 0)
            {
                return PathProgressionStatus.COMPLETE;
            }
        }

UPDATE

If I do keep track of how much force I've applied, it fails to account for other forces that may act on it.

I could use reflection and set _force to zero directly, but that feels dirty.