You can "hold" on to him all day, everyday, as long as you are doing it from a state of already having it. I think of my boyfriend ALL day because I love him, and if doubts arise, I make them go away. I know that if I entertain negative thoughts of our relationship for too long, they can manifest because I get lost in that state of disharmony. It takes a bit to get used to, and we all fall back sometimes into our icky thinking, but we have to continue to monitor our thoughts and feelings and keep them as positive as possible.
"Hearing" him say what you want is always an awesome experience and you don't need to imagine him standing there if you don't want - you can just "hear" him say what you desire him to say.
I think looking for articles and such on how to improve a relationship or get someone back is one of those things that will hinder any progress because you are coming from a state of not having it.