Some people have a sense of "calling" to a particular work; others just find something that seems to make sense for them. Others just make a living any way that they can find, and leave talk of "callings" to those who have the luxury to choose.
I am a person who had a very overpowering sense of "calling" when I was almost 20 years old. And, the sense of purpose coming out of that helped me to organize my thoughts and feelings in response to that call.
Psychologically speaking, adolescence and young adulthood is a natural time to experience a sense of calling, because it is in those years that we are struggling to form our adult identity. Some young adults are able to maintain or establish a positive sense of self and then find a job and learn how to live as adults in this world. But, some young people, like me yearned for something more. Maybe part of it was that I had the luxury of choices, since I was not desperate to put food on the table.
I am deeply thankful for the experience of feeling clear that I was to work with people who were in trouble, and to go into dark places with them in the name of God. I responded by transferring colleges, majoring in religion, reading a lot of theology,philosophy and Bible, and trying to make sense of things theologically and spiritually. I responded by deciding to go to seminary. I felt called to find out the truth, proclaim the truth and live the truth. And, that truth from God that I felt deeply had to do with standing with people who were down or cast out by others. It is this calling that has gotten me through a lot of confusion in my life, has carried me through times of self-doubt and sorrow, and that continues with me like an old friend at this point.
Of course, sometimes we get tired of old friends, and long for some new friends.
Though I do get weary of dealling with trouble, I am deeply thankful for this sense of purpose in life. I am not the kind of person who would adapt too well to societal expectations of adult life if I didn't have some individual sense of purpose.
As I get older and as I get tired of dealing with responsibilities and people's problems, and as I think of how great it would be to have a long,long vacation (maybe retirement) from dealing with people in trouble, I have to look at my old friend, my calling, who stood with me and held me up when I didn't have the strength to go on, who told me I was worth something when I felt so down, and that made me realize that my deepest purpose in life is not to be happy but to serve God - the God whose heart goes out to the poor, the downcast, and the outcast.
It has been my experience that happiness comes as a second thought, as a by-product of purpose. "Seek you first the kingdom of God and God's righteousness and all these things will be added unto you as well." If you set out to be happy, happiness usually remains out of reach. If you set out to fulfill a purpose, then happiness may not always be at the forefront, but it sneaks up on you again and again when you least expect it.