I've been using the same beta reader for awhile now, but lately my reader hasn't been available for my newest book. I stopped freaking out about that around the same time I learned a valuable lesson about writing. Beta readers and reviewers are great, but as an author you should always be trusting yourself...and so should I.
The Issue of Trust
It's good to have beta readers, to get a second opinion, to check your work against someone else so you know you're on the right track. But you can't always rely on these things. The actor writing a novel is always a risk. It's a leap. You're putting something out there that's personal to you, and the world may rip it to shreds. You'll get a little less bloody if a beta reader rips into you first. But you don't always get that option. That's why you always have to make sure you're trusting yourself...and your book.
You should be critical of your own work, give it a careful edit and pay attention to the details. But at some point, you have to stop polishing and worrying -- and start trusting yourself. You don’t always have to wait for approval from a beta reader or an early reviewer. Sometimes, it may not be possible to get that stuff.
So find a way to trust yourself and your book, because you have to trust yourself to write it. If you aren’t trusting yourself, you aren’t presenting your best storytelling. So however you have to learn it, no matter which part of the process that tests you, learn to trust in you. Your writing will be better for it.