Sentence Construction

In isolation it is a bit hard to understand the exact intention of this sentence, or even to be certain that it expresses a complete thought. I think you may need to provide more context.

The intention of the sentence, sir, is to say that it's not just the possibility, the mental aspect of it weighing me down, my fear of it, but everything that stems from it, the logistics of it, my preparation for which is also a source of stress.

Respectfully,

Samir

Ty.

Unfortunately I think it is not possible to comment with confidence on this sentence without seeing the surrounding text. The sentence does not stand alone successfully. It may or may not work in context. The context needs to provide the information that would be contained in what seems to be a missing "that ..." clause at the end. For example: "So it's not just the possibility, but everything I d

Also, it is not very clear whether the second "it" is intended to refer to "possibility" or to something else.