It is usually very hard and takes a long time.
I was kicked out, excommunicated, and declared a "suppressive person" in 1982. Yet, at the time, I didn't agree, and I tried hard to be taken back. It wasn't before about a year later that I realized that I was much better outside that organization, and I wouldn't want to ever be a member of it again.
At that time, I was essentially still a Scientologist, just one that had disagreements with the way the organization was run. It took me another number of years to get over that and consider myself an ex-scientologist.
Leaving the organization and leaving the subject are two different things, but typically tightly interwoven. One is afraid of leaving the oppressive cultish organization because one is afraid of letting go of that whole manner of thinking and that body of material which is Scientology.
I could talk for hours about my experiences, so it is hard to put into a brief message. Leaving the Church of Scientology is probably similar in many ways to leaving any other all-encompassing religious type of organization. You know, one where most of your friends and family members are members, and so are your business partners, your employers, etc. Where it guides what books you read, how you interpret the news, how you plan things, which things you plan on doing, etc. It is so all-pervasive that it is very hard to leave. If you do, you have to come up with new ways of doing almost everything. And if the tradition in that organization or religion is to shun people who leave, all the worse, you have to find new friends, maybe even a new family. The escape velocity is very high. You really need to gather yourself together to leave. Or you have to be thrown out quite forcefully before you really leave.
But ultimately, it is very freeing to leave an organization that tries to control your thinking. It can be a very healthy process to sort out for yourself what you actually think is true and how you want to think and feel. The more the subject you're leaving has pretended to have the answer to everything, the longer it takes to sort through. But it is worth itMore questions on Scientology: