Sorry LP. I disagree with that explanation. In still air (unlike my example) the acceleration is lateral, not in the direction of flight (mechanics of circular motion). Imagine any object rotating on perfect bearings (no friction or drag losses); it will rotate forever - it will not decelerate because of the apparent change of speed you describe.
In still air it's purely about the inclination of the lift vector and the increased drag that results. With wind the momentum effect, I mentioned also comes into play.