Simple thing: faith.
Zechariah doubted and become temporarily mute.
It seems so hard to have faith. Doubt is a much easier route, such as with Sarah and Zechariah. Surely it's not simple. There's so many things to consider! Namely, it's hard to put your faith in something you can't see. In fact, the idea is crazy, right?
Think about a traffic light for a moment. Imagine you're in the protected left lane and it turns green. How do you know those cars coming towards you are going to stop? How do you know their light is actually red? Faith. A whole lot of faith.
Faith in God is kind of the same way. Sometimes it seems dangerous, but we know from experience it works. My brother is going to be getting his driver's license soon. As a driver rather than a passenger, he doesn't have much experience to trust the system. Instead, he has to trust his teachers - our mom and dad - who do have experience. Again, our faith in God is like this.
Ultimately, you must decide to have faith on your own, but listen to those you trust. Watch their lives. What makes them different? Often, it is faith. Let your peers and mentors be a beacon to you.
Let me add, this is not faith in some distant, removed deity. It's a faith in a God who came to us as one us, Emmanuel. He understands you as your Creator and as a human. He died and broke the curse of death by rising again. He did it for you. This is the God I put my faith in. I hope you will too.