It takes a lot of soul searching. The physical clutter is easy…if you look at something and realize you haven’t touched it (or looked at it in the context of some decoration) in 6 months, or maybe a year, it isn’t really that important. Some things have immense sentimental value, but that is different.
The attitudes, fears, etc are a different matter. You have to look honestly at all your attitudes, fears, emotions, etc and think about them deeply. If you are afraid of something, think about what it is that actually scares you. If you find yourself being angry or sad a lot, try to look at the times (things that are going on in your life or events that you have touched on) and see if there is a common thread there. Try to eliminate those things. For example, if watching the evening news always makes you feel blue, stop watching it.
You also have to have the understanding that all these things that constipate you mentally and emotionally are keeping you from actually enjoying life. Let’s say you are dreadfully shy. I used to be this way. You go to a party and have a hard time talking to new people or participating in the “fun” things. This shyness is usually some form of fear. You are afraid of what others will think of you, you are afraid you will make a fool of yourself, etc. You can consciously force yourself to interact. Speak up when you talk. Say hi to a stranger. Do something that has a high chance of making you look foolish. You will find that all your fears were baseless. Yes, some people will not like your views or will laugh when you do something foolish. You can’t control their reactions. And you can laugh along with them because it probably was funny. I they are bringing arrogance and ridicule if you do small things “wrong”, they have the problem, not you.
In the end, visualize what you want to be like and behave the way that will get you there. And you might just find that people you now believe will drop you, will actually be more drawn to you.