You have to go back and see what excited you from childhood onwards. What did you visualize yourself to be? What are the fields that you showed interest in? What did you want to become? Write all this down. Repeat the exercise after a fortnight without referring to your earlier points. When you repeat this 4 or 5 times and compare the notes, you will find that one or two things keep repeating. Zero in on the stronger among them. This is your svadharma. Then in your Svadharma, fix a higher ideal.