Has it given you a medical condition so you can't spend quality time in which to address your issues? Are you not being able to progress in your personal relationship because physical things are being put in your way to prevent you?
The reason is - and there's a reason for absolutely everything - because you are not being brave, and facing your most private fears and issues, your Self is helping you to stay back in the illusion. It makes us think things are physical – because your issues manifest in your physical body.
We need to address our issues, our fears - the fear of facing them anyway, and they will very quickly go, and so will your physical conditions. I tell a story about my very bad throat and cold for 6 weeks, time off work, really poorly, when I suspected my ex boyfriend was having an affair. I was really ill because of my mental state! But as soon as I addressed it with him (which I was putting off because I knew would mean the end of our relationship) my throat cleared up overnight!
Do you ever sit alone and cry? Many of us do. I've done this, but I don't do it anymore. Well, I soon snap myself out of it if I feel it coming on, because it is purely me feeling sorry for my Self. It is negative and a waste of energy. It doesn't achieve anything, if you think about it, does it? All it achieves is a sad feeling that “I am hopeless”. However, we know differently, we know that we can find a solution to every problem - that's why they are problems - to be solved! Challenges to overcome. We need to be strong to overcome our challenges.
It's up to each one of us.
So “How to stop feeling sorry for your Self”? Understand what is happening and that you're not achieving anything when you're feeling like that, and then make your mind up to react to your problems in a different way.