How do I decide my field of interest in life?

 I am an Engineering Graduate in Electrical and Electronics Engineering and i had been through the same situation.

After i completed my 2.5 years of Engineering, i came to know that Electrical engineering is not my cup of tea.

I started looking for options and i found Banking as a good option with plenty of opportunities and hence i started working in that direction.
I was doing great but results did not came into my favour as i missed my 2 exams by 3 and 1 marks respectively.

I was again devastated.
But during my engineering when i used to read articles or watch movies or some kind of videos related to computer science, programming was the part that always excited me but i used to be very dumb at them.

I took a deep breath and analyzed the scope of programming that i can carry and after certain research i came to know yes this is my field of interest and now i am learning successfully and doing good till now.

so what i want to say you is that to know your interest, you got to try some thing that excites you at least.

You may fail in once or twice but you will gain knowledge and that knowledge will give you experience too.

You would be able to judge the things properly.
the Biggest advantage you have got that you are still in the first year and you have got plenty of time to try and analyze.

Just go for any thing and try your luck.
You will surely find it out.

All the Very Best Buddy and feel free to ask any thing. :)
Hope this will help you in certain way.