When we meet new people, one of the first questions we ask is "What do you do?". I don't know if it's universal, or particular to America, but we have a tendency to define ourselves by our occupation.
God isn't concerned with the same things we are. About John the Baptist Jesus said:
Matthew 11:11John's ministry lasted for perhaps six months, and here Jesus says that he was greater than any of the prophets, judges, and heroes who had come before him. Why? Because John accomplished more? No. Because John became the man God wanted him to be.
I tell you the truth: Among those born of women there has not risen anyone greater than John the Baptist; yet he who is least in the kingdom of heaven is greater than he.
God doesn't care about what you do nearly so much as he cares about who you are. In most cases, there are a myriad number of jobs you could hold that would all be pleasing to God (I don't believe God "calls" us to occupations). There are a great number of people you could build successful marriages with. There are innumerable places you could eat lunch, all of which would be equally pleasing to God. That's not to say any decision is correct, but there generally isn't only one right choice.
What matters more is who you are. God doesn't need any of us to do his work -- he can do anything he wants, all by himself -- but he chooses to use us. Not because he needs the work to get done, but because in the process of working for him we become more like Christ.
Consider also the account of Jesus' visit to the house of Mary and Martha.
Luke 10:38-42There is a great deal of work to do, but only one thing is needed: to sit and listen at the feet of Jesus.
As Jesus and his disciples were on their way, he came to a village where a woman named Martha opened her home to him. She had a sister called Mary, who sat at the Lord's feet listening to what he said. But Martha was distracted by all the preparations that had to be made. She came to him and asked, "Lord, don't you care that my sister has left me to do the work by myself? Tell her to help me!"
"Martha, Martha," the Lord answered, "you are worried and upset about many things, but only one thing is needed. Mary has chosen what is better, and it will not be taken away from her."
Don't spend time trying to determine what God wants you to do. Focus all your energy on becoming the person God wants you to be: a person who looks amazingly like Christ. As God builds the character of Christ in us, we will naturally and necessarily do what Christ would do in our place. We will do the work of God as we attain the mind of Christ. Attempting to serve God otherwise, in our own power and by our own will, is futile.