Apparently, there are all the answers to life's questions in the Eastern culture. But at the same time it's not always easy to reveal it. There is also a special term in the Japanese language that covers all the elements which could help you to realize that you've made the right choice, but the elements must be combined.
The word is "ikigai". Complete meaning of the term is quite hard and detailed but it worth comprehension.
Probably you've read something from the ancient philosophers and maybe even modern psychologists whose books in bright snazzy covers are promising you all the answers and useful information on how to be happy and find your vocation. I'd be glad to receive some experience from after reading those books.
But it seems that the answer to the question in the title is very simple. If you wake up every morning in a positive mood, if you cheerfully go to work and do your best every time and then repeat the circle the next day - that indicates you've made the right choice. If you feel like the work is done efficiently and well, if other people are admiring your results and everybody is using your fruits of labor - you've made the right choice. If you know what "inner satisfaction" is and if you willingly share the experience and knowledge and people need it - you've made the right choice. If the income from your business isn't the determining factor and the main motivation for your work - you’ve made the right choice in your life.
Finally and most importantly - if you feel that you've made the right choice in your life it means you are almost a happy person. I'd say this is the reason to be proud of yourself and to get some lessons from you.
I hope that everybody who has read this note is a happy person who have found the right way and keen to share this priceless experience with others.