Ambivalence keeps us stuck in that stage for years sometimes. To move on, we must ensure that the advantages outweigh the disadvantages. If you only list 5 or 10, keep looking. Consider the social benefits of physical activity. Put the fun back into exercise.
Exercise carries more images of martyrdom and boring routines than fun.
Call it something else, like active living, or fun walk, or activity night, whatever strikes your pleasure chord. Imagine a flow of fresh air and energy circulating inside your body. Envision loosening those stiff joints and filling your lungs with life-giving air. Or renewing the supply of oxygen to your overstressed brain cells. Think of three ways you could reward yourself for increasing your activity level.