Everybody - at least everybody in the publishing world - knows about waiting.
For many, the worst is when they submit their queries to agents and have to wait for a response - often a rejection, but eventually (at least that's the aim) a request for partial, full or an offer of representation.
Then comes the wait once your agent submits your MS to publishers. And, believe me, that's can be a long wait, and something that you have no control over. It might be a week, a month or a year before you hear anything - if you hear anything at all. It's a wait I don't think you can ever get used to, but you have to accept that it's just the way the business works.
But there's another wait: the wait for feedback from those much closer. At the moment, that means waiting for the beta-readers to comment on the latest MS. Is it worse than the other waits? Probably not, but it is difficult, because this is the first time you'll hear any comments on the viability of the work. I'm sure most writers are wracked with fear that everything they produce is garbage, and we are fragile souls, so we need (I mean, really need) that feedback.
You can't rush it, of course. These are, in the main, people who are doing you a favour. They're not being paid - except for being given a free book - so when they say "I'm reading something else, I'll get to it next" or "I'm away this weekend, I'll look at it next week" or "I had the kids last night, didn't get a chance to read it" there's nothing you can do except smile sweetly and mutter with as much conviction as you can muster "That's okay, no rush" while dying slowly inside from a terminally neglected ego.
I doubt it will ever get better. When (not if, you understand) something gets published with the Marshall Buckley name on the cover, I'm sure the wait for reader feedback (and, hopefully, reviews) will be just as tortuous. I suppose this is just practice for those times.