I think everyone experiences this.
Human beings naturally resist change. So, a change of any kind, whether relationships, jobs, locations, or lifestyles, can lead to second thoughts and doubt. Think of all the people who got cold feet right before getting married. It is perfectly normal.
As a member here used to say, everything you have ever wanted exists just on the other side of fear.
The key is to finally decide what you want, then set aside those doubts and go for it. It isn't easy. The hard part is making that decision.