I actually think that this part is worse than looking for jobs. For complicated reasons I quit my old job, and am now job-hunting. My hit rate so far is not too bad: four interviews from seven applications, but the wait to hear the results of an interview is the stressy bit. The interview might apppear to have gone well, but you still get turned down. In my case, two so far, one a surprise, the other less so - one person who got a job there is someone I trained. I've got a second interview for one job, which is more stressful than a first, as now the stakes are higher. Then's there's the nightmare scenario where a job you don't particularly want offers before the people you do want...
All that said, back in 2012 when I left the FSS it took seven months, 196 applications (with only six leading to interviews), and a move of 180 miles to get a job, so there are worse things in the long term. But it doesn't seem like that when you wit for the call.
The waiting game can be a pain, but only because you create so many varieties of the scenarios that could play out & especially when we are feeling the need for something so important; our base income, potentially even in the worst case affecting the roof over our heads, the food on our plates and whatever other commitments we've made that we've taken for granted until presented with such a scenario, our brains have a very bad habit of creating a whole host of unpleasant scenarios which of course grab our attention & then the unpleasant feelings linger.
Even if you're in a good position where you don't have to worry about those needs for a good few months, maybe even years... we still seem to run through those scenarios anyway - only projecting them a bit further in the future.
When you're on the cusp of freeing yourself from these concerns, they have a nasty habit of amplifying... waiting for the answer is usually one of those times... much more so than the build up to the interview.
Your reality is often less serious than what goes on in the peculiar recesses of our twisted minds... still haven't quite figured out why our minds like to torture us from time to time, maybe it gets a kick out of it
Best way to chill out and dial it out is to get active... go out and do things that require both physical and mental interaction... something that demands a level of focus... even if it's just going to the park to throw/kick a ball around or a handy hobby that has no/low cost associated with it, that light focus can help quite a bit. Ideally something you enjoy, even better if it has a feeling of familiarity... then you get a moment of normal back which gives you some breathing room.
Try not to kick yourself too much, it'll work out.
As for various offers coming at different times... if the one you don't want offers you the position and you're hopefully waiting on a response from your preferred option. It's perfectly normal to ask them to give you a bit of time to consider your options, you can ask them what timeline they would prefer to receive your answer & even be open with them and let them know that you are waiting on another option and as it's all in progress, you would be doing yourself a disfavour by not considering all the options that have been put in front of you. It's just business for them, it's a significant life decision for you... most will understand and give you time, some may appreciate your candour and one that's really keen on bringing you onboard may even come back to you with an increased salary offer. Don't expect that last one, but it is possible. If it's your less favoured option that pulls a salary hike out of the bag to bring you in, you might like to take a closer look as it's possible it might be a nice environment, after all.
If you find yourself in that position & the company you ask for a bit of time to consider your options declines your request and demands a quick answer... you generally want to turn them down... although you need to read it on your own, because it's also possible that they have a significant gap in their team & need someone as soon as possible and if you're possibly going to decline their offer, then they will quite quickly get in touch with their second choice before they accept another option and they risk having to restart the slow and arduous recruitment process, but a better company with such a need will usually head back to their first choice with a higher salary offer... as long as their accounts will approve it.
Also, even if you accept an offer & then later on, before your start date, that offer you really wanted comes through lands... you can still change your mind, just communicate with them and there won't be any significant hard feelings. It's not an ideal position to be in & it can feel like your breaking your highly held honour in doing that... and perhaps if you were making such a commitment on a person-to-person level, then I would likely recommend following through with your commitment. But you have to put yourself in the frame of mind where the outcome of this deal is directly important to you on a personal level, whereas to the company - it's just business & it will not cause any significant problem to the company or the people you were interacting with as representatives of the company, you are not causing any harm by acting in your best interest & they will understand.
I have been on the company side of that exact scenario not so long ago and neither the MD nor I held any ill will against the person. Just remember it's personal for you, it's a business deal for them.