I'm just wondering, how many times have people actually said something about your nose? Or expressed something which you certainly know is about your nose? (like pointing at it, or making gestures etc)
Is your feelings related to some bad experiences as a child? As a teen?
Have people in recent years said something about your nose?
If you want to change your believes you gotta let reason rule over emotions.You gotta try and look at the world 'clinically', and think about your experiences, and ask yourself if the believes you have actually conforms with reality.
On a day to day basis you can't of course investige every instance to find out if a person has a negative opinion about you, but you have to like "take a breath" and ask yourself "do i actually know?" You know, do a quick analysis of the situation and ask yourself if you have enough evidence to back up your interpretation of what happened.
As to obsessing with something, the only way to do that is to try and let it
go and focus on something else.The mind seems to work in such a way that you can't forget something if you "tell yourself to forget it".It's like saying "don't think of your nose".If you say it, you'll think about it.You have to find something else which you can be genuinely interested in to focus on.
Constant negative thinking and obsessions actually enforces the negative believes.If you go into these long periods of obsessing with something, and invoking great emotions in yourself, you are actually making sure that you will remember it in the future.
I have these idiotic negative thinking sessions myself, but sometimes lately
i have managed to stop myself.And the reason i have managed to stop myself is that i had a "clear moment" and asked myself "is it actually worth it?"
You can look at the times in the past, when you might have gone hours and days thinking about something, and ask yourself "Has anything of value come from all that thinking? Is there anything good in my life which has come from it?" My only answer is that it has only served to make me feel really bad at the time, and perpetuated my own irrational beliefs.
And if you realize that nothing good has come from it in the past, then nothing good can come from it in the future, and it might be easier to just let it go.