Resizing Character controller?

i want to resize my character controller when my player lands. i wrote the script like this:

     if (anim.GetCurrentAnimatorStateInfo(0).IsName("land"))
     {
         speed = 0;
         cc.height = 0.9f;
     }
     else
         speed = 3F;
         cc.height = 1.8f;

it sometimes works but sometimes doesn't. why and what is the way that the controller may probably be resized?