I do not feel it anymore
I have been working for 15 years in this company in the same position. I feel like moving on and exploring new things. I want to achieve something more than what I have right now. I am gonna resign and follow what I want. But my boss won't let me go. They said that I am the only one who knows to run the business.
Working for a company is a choice and not a compulsory decision. Some people tend to be bored with what they are doing for a living. Doing the same thing for several years while note enjoying is not healthy. You can resign if you want. If the company you are working for is holding you back to resign, they must have a reason not to let you go. No one should hold you on resigning unless you violated a rule.