Giving myself permission

Hi coaches,

I am am currently fasting and every day my brain jumps into fear and freaks out sending all sort of negative thoughts. The experience of fasting becomes excruciating because of my resistance to all of this: sensations, thoughts, feelings. I spend daily lot of time in practicing allowing, and sometimes I can open up to what is, but then I go back over and over to resistance. Now, one simple solution would be stop fasting, but there are some advantages of it that I like and above all I would like to gain a more mature relationship with it, so the version of me I aspire to is not as reactive as now. So I am keeping this daily river of misery in my life with the idea that approaching this experience every time from new angles this resistance will finally fade away.

Now one of the approaches that I like to use is to try to give myself full permission to fast and to not to fast, with the idea that expressing a choice feels much more empowering than obeying a rule. I am not sure though my brain is really convinced that I am giving myself full permission.

So, how do we give ourself full permission in a way that is not perceived as me trying to fool myself? How do I fully believe I am giving myself 100% permission without showing it with an action? Rephrased in a different context, how can I believe I am giving myself full permission of eating a cake without the need to go and actually eat it to build evidence supporting the belief?