Indeed. Deep shame makes you believe without beating yourself up you can't actually reach results. Lately, feeling deeply inside of myself I have noticed the diference.
The wall between us and what we want to do to improve is not made of stone, but some sort of very cold water. You can erode yourself by grabbing a hammer and strike the wall while getting inside it or you could just step inside. If you just let yourself feel the unconfortable cold you it will vanish in a while, most of it at least.
Another trick I use is saying "This is all there is", to let my mind know I won't budge from what I am doing until I finish it. That way it stops trying to distract me while I write. You know, these thoughts of "Let's check whatsapp real quick, let's watch facebook real quick, let's grab a soda real quick".
Right, I think you've said it quite well with the analogy of cold water, it puts you in a state where you're disconnected from what really matters and you try to come up with all sort of tricks to stay in that stage instead of knocking yourself out of it through admitting that this is all there is and you need to get it done and experience it right here, right now.
I think the modern world brings so much excuses for us to justify our lack of willpower with regards to our thoughts and emotions dictating the way we live our lives.