Can you change your subconsciousness by repeating sentences?

Factual Questions
1

I have agoraphobia and a way too strong reaction to the sight of blood, I think it’s called vasovagal response, in ancient history some people had that and basically that response tells your body to black out (lose consciousness) when you see blood, as this would have acted as a defense mechanism and saved you from ancient animals or whatever, basically your body’s version of “act dead”.

Obviously there’s no more wild animals hunting people and no reason for this, but a percent of people still have a strong reaction to blood and lose consciousness, like me for example. While I was still in high school some 4 years ago, I saw blood and lost consciousness once (and woke up to 30-ish students staring at me) and the second time, which was just a few days later, we had a medical lesson of some sort and the professor was telling a disgusting blood related story and I fell out again, even though I didn’t physically see blood, but just imagined it…and once again, I was surrounded by dozens of students when I woke up a few moments later.

Since then I have agoraphobia, which is an irrational subconscious fear of large groups of people, I connected blacking out with large groups of people and now I get a slight panic attack every time I get in a situation where there’s a lot of people around me, I don’t have a real attack like epilepsy or something, but instead an “internal” one, my blood pressure starts falling low really quick, then that scares me even more and I start breathing really quickly and I risk maybe really blacking out again, even though it didn’t happen even once since 4 years ago, but I have these panic attacks every month or two, sometimes even more frequent, mostly when I’m in a supermarket, public transport,etc.

So, if I repeat to myself that nothing bad will happen and that I should just calm down, will that eventually help me beat agoraphobia? Or maybe even the blood fear later on?

There’s some additional things I really need to change about my life, I’m really lazy and non-productive for example and perhaps subconsciousness has a lot to do with that as well.

2

I can relate to what you are talking about. Blood doesn’t bother me but the crowd thing does and I have a lot of signs of agoraphobia. I tend to live in a very small world. I was on a trip with my family one time and we got word that our close friends were killed in an auto accident. 3 children and the wife died but the husband survived. It triggered panic attacks in me whenever I was on a long drive with the family in the car. It took a few years but I was finally able to convince myself that when the attack started all I had to do was ignore it and it would pass. I had always worked though these attacks with no one knowing about it but me and it was extremely uncomfortable. I would make excuses to pull over for a few minutes. The crowd thing I have not improved on much, I don’t seem to have much desire to want to fix it. If I have to be in a crowd I just make sure I stay on the outer edges.

As for the lazy unproductive thing, I was able to make a complete turn around in this area by simply starting off with small tasks and making sure I finished everything I started. It took some discipline at first but after a surprisingly small amount of time the simple joy of completing a task well done motivated me to take on more tasks. I was always a good worker at work but a procrastinator on my own time. Now I am on the opposite side of the spectrum. I seldom put off anything and finish everything I start.  I am convinced we can rewire our selves.
3

It might depend on how you do it. For example, if you repeat to yourself “This won’t happen” while vividly imagining traumatic things happening, that may well backfire.