When you finally got promoted, you thought that you'd finally be happy. But, there's the next level or the next promotion to strive for. The bar was raised.
When you finally had a business breakthrough, you thought that you would finally feel fulfilled. But, there's an expansion to look forward to. And also other business opportunities. The bar was raised.
No matter how much you have achieved, the bar always seems to be raised higher.
As long as you keep looking at other people to define your success, you won't be happy or feel fulfilled—no matter how much you have already achieved.
Success is relative.
Don't measure your success based on how others are doing. There won't be a scarcity of people who will be doing much better than you are doing.
Measure your success based on how you are doing. Are you doing better than yesterday?
Measure your success based on how much you're helping others. At least, someone. Are you?
Go at your own pace. Comparing is a no-win situation.