Do we have to have one desire only? Or having more is perfectly normal? How can you find out your truly one(s)?
You need 3 things:
Passion: write down all of your interests, make a list. Having more than one passion is a gift not a mistake!
Learning: search what you need to learn on that field. Changing your interest and starting over is a brave thing! Do not care about your age, start something new if you feel it.
Adaptability: use your information and different skills anytime. Having various passions, interests and skills are helpful to step out of most situations. Knowing only a little in different fields help you to solve a problem on a wide scale.
Do not afraid of having a lot of interests. You can change your plans and careers anytime you want. Wrong time doesn’t exist.