How do you find your spark?

I have always wondered how some people just know what they have always wanted to do. The certainty and the determination, how do you find what's your passion? What you are meant to do in life? I thought i always knew what I wanted which was veterinary since I have always loved animals but now that im older, I don't even know if that's what i want. I don't know for certain. And I'm so scared that I might regret not doing it but at the same time, I'm scared what if i regret doing it...? To those who ended up doing the dream course, did you regret it? And to those who didn't, do you regret it? I just wish someone would tell me how to know if that's really what u are meant to do coz I am so lost. With the upu phase opening up soon, I am just so confused and indecisive.