I heard a pastor say...
"If you want to find your calling, start by looking at what you hate..." He was speaking of how those little things that bug you are thigs you are called to change. For example, if you are at church and feel the music is off, you are probably called to serve in the music area of your church, likewise, if you are irritated that things don't start on time or you are late for something, you're probably called into some sort of administration.
I've seen this...during the praise and worship, my husband would hear little things in the sound that needed to be changed. Not everyone else would recognize these things. He also could tell me exactly what the problem was and how to fix it. Let me tell you what he does at church now...he is on the Sound Team.
If you are looking for your purpose, your calling, look to the things that seem to irritate you the most, see if that is where God is calling you to be!