I think one of the hardest parts of being a writer is the waiting. You wait to hear back on submissions, wait to hear back from beta readers, wait for checks to arrive, wait for books to arrive, etc. And if you're anything like me, waiting is probably not your forté. So what do you do to get through it?
Here's a few suggestions:
1) Keep multiple projects going. Once you send out the latest manuscript to your betas or a slush pile, get to work on the next one. Okay, you can allow yourselves one evening to celebrate your satisfaction, but, after that, back to work. After all, even if this one gets accepted, careers don't happen on one submission. You have to keep building your business.
2) Regard it as a business. All too often I meet writers who talk as if their writing is a hobby, yet act as if acceptance or rejection is something their life depends on. I have few friends whose hobbies are so important to them. If you're that invested, it's not a hobby, so stop pretending it is and treat it like a business. Work on your craft, including writing classes, reading a lot, studying what other writers do and how they describe their own craft and struggles. Set up a database for you submissions and your income and expenses. Treat it like the business you want it to be.
3) Blog about it. That's what I'm doing and it's therapeutic. There are lots of people going through the same thing and sharing with each other is an encouragement and learning experience.
4) Remind yourself that finishing and submitting your work puts you a step ahead of many others. Lots of people say they are writers or want to be, but only those who actually write, complete it and submit it have the chance to actually make it as professionals.
5) Offer Reader Incentives. This one won't work with the markets you submit to, but it might work with your beta readers. Of course, it all depends on your budget. But think about running little contests with your betas for the person with the most helpful notes, the quickest response time, etc. You can offer everything from gift certificates for a cup of Starbucks to writing lessons or services. It might be a way to keep your betas motivated. After all, if they're not writers, they probably don't realize how hard the waiting is or how important their input is to your success.
Everyone's situation is unique, so I'm sure you can think of better ideas than I can. See what you can come up with to make the wait time pass more quickly. Whatever works for you might not work for me. The point is to use the time to further your career, instead of regarding it as holding you back.
Good luck with your writing.
For what it's worth...