Just wanted to throw in my two cents on the subject of stage fright and fear of bothering neighbors when practicing. Like many of you do, I live in an apartment, and I am hyper conscious of irritating my neighbors, and I've probably got a clinical level of anxiety anyway. Ah, what can you do but laugh...
Here are some solutions that have helped me.
1. The Beltbox
The Beltbox has been mentioned by many people on this forum. It's a great little sound dampener that fits over your mouth and cuts the sound by about 30 decibels. These days I only use it if I want to do something way too early or way too late for me to reasonably expect my neighbors to be awake, but in the beginning it was a LIFE saver for letting me practice in my apartment instead of in my car. They recently redesigned the Beltbox to be a little roomier and the model I got hasn't limited my ability to open my mouth at all.
2. Ask your neighbors
Ask your neighbors what hours would be the least irritating for them. For me, turns out the only comments - not even complaints - I've ever gotten from neighbors are "you have a beautiful voice" lol
3. It's all in your head
Realize that in all likelihood a lot of this is in your head and has nothing to do with your neighbors haha Personally my realization went like this:
Just ask your neighbors if you're bothering them.
Yeah but then they'll know I'm singing.
Oh so THAT'S what you're afraid of lol
Now I just remind myself, Kai, you plan on being a singer, they're gonna find out anyway haha SO JUST SING
4. Getting comfortable in front of people is its own skill set
I also know from ten years pursuing a career as a dancer that practicing and performing in front of people is an entirely separate skill from doing your thing well.
If you haven't been practicing in front of or within earshot of other people, then when you finally do, you should expect to lose about 25% or more of your skill level until you get used to it. It's just what the nerves do to you.
I remind myself, "Before you can do it well, you've got to do it at all." That includes singing in front of people, or at least where they can hear me. So I push myself to do it and do it often, and I remind myself that before I can expect myself to do it even reasonably well, I've got to be doing it period.
5. Discomfort challenges
Give yourself discomfort challenges. Start small. Maybe that's saying hi to ten strangers. Maybe that's singing in front of a friend in your living room or hitting the karaoke bar. Maybe that's posting a demo for feedback, no matter how rough you think it is.
Personally, about once a week I've been going with a friend to a small outdoor amphitheater in the middle of a park near my house. We practice there for about an hour. There are LOADS of people walking through this park all day. It is insanely nerve racking. But I'll tell you what. After doing that, the karaoke bar seems like a BLESSING haha
Those are some of what's helped me a lot over the last several months. Hope it helps someone! And if you've got your own strategies, would love to hear what has helped you