Being afraid of sharks is one of lifes natural reactions. But in my experience the sighting of your first shark brings a completely different reaction to what you would expect.
I have taught many people to dive and as I live in Malaysia we have sharks. I try to take my students on their first dive after qualification if possible, also we have some qualified divers who have never seen sharks. 99% of divers on seeing their first shark (doesn't matter if it is a reef shark or a hammerhead) start to chase after it! Most sharks you encounter will swim away from you, unless you do a shark feed dive! They will sometimes let you get within a foot or so if resting on the bottom, but usually no closer.
We as humans are curious creatures and most learn to dive to find out whats down there. So the first time you see a fish, nudibranch, crab, lobster or whatever, you have never seen before your first reaction is to take a closer look. No matter how many years of diving you have under your belt this is a natural human reaction.
Please enjoy your diving and don't worry about anything. Pick who you learn to dive with carefully. A good instructor as well as teaching to dive will show you some of the wonders of the wonder water world. Once qualified the worlds oceans will be calling you. There are so many places to dive in many different conditions each with it own beauties.
Have fun!
