What exactly is it that you start panicking about? First off.....you're okay. You have air to breathe. And plenty of it. You control your depth so you can stay as deep or as shallow as you want. If you ever want to dive somewhere like Cozumel, you'll want to dive to at least 40-50 ft (12-15 meters) to see the reef and all the life that inhabits it. You never really need to go deeper than about 18-20 meters (60-70 ft) to see the majority of the sea life you want to see. So if it helps, maybe try to work yourself down to that depth. And yes, in an out of air situation it is possible to swim back to the surface from that depth. Not something you really want to do unless it's absolutely necessary, but it's certainly possible pretty easily. So not something you really need to be thinking about during your dive. Certainly not a bad idea to know how to self-rescue should something go wrong, but don't focus so much of your energy on worrying about something going wrong. Thousands of people make multiple dives on a daily basis and there are in all actuality very few diving accidents in relation to successful dives.
Try to remember two key things during your dive:
1. Always Be Breathing. Never hold you breath
2. Take your time. Don't be in a hurry. It's not a race.
Take your time during your descent and don't get in a rush. Descend a little bit and stop when you start to feel a little uncomfortable. When you start to feel okay, maybe descend a a little deeper and stop when you start feeling uncomfortable again. Do this over and over until you're comfortable at whatever depth you're trying to reach. Just try to remain calm and relaxed. Diving is supposed to be exactly that. Don't give up on it! You Can do this!
