Overwhelm is downright nasty. Few things cripple otherwise productive, creative, and enterprising people like being overwhelmed.
The worst state of overwhelm is probably when you start feeling like you're "shoveling sand in the ocean." It's when you're far behind schedule, but it seems like even working at maximum efficiency and intensity for an indefinite period of time won't make things any better.
It's an ugly place to be.
There's not so many ways to deal with it. Thankfully, they're pretty straightforward:
1. Triage / Work-bankruptcy: Declare that of some overcommitted projects, you're going bankrupt and cutting all but the most effective ones. If your email inbox is overflowing, you skim it very quickly and star the very most important ones (and only those, very judiciously), and you archive the rest.
2. Break down progress into manageable measurable chunks: In the above email example, say you've got 3000 emails in your inbox. Overwhelming. To get up to speed, you might define out these stages:
-- Down to 2500 emails
-- Down to 2000 emails
-- Down to 1500 emails
-- Down to 1000 emails
-- Down to 700 emails
-- Down to 500 emails
-- Down to 400 emails
-- Down to 300 emails
-- Down to 200 emails
-- Down to 150 emails
-- Down to 100 emails
-- Down to 70 emails
-- Down to 40 emails
-- Down to 20 emails
-- Down to 10 emails
-- Inbox Zero
Yes, that's 16 steps. That doesn't mean you need to stop if you get ahead of schedule. But if you nail down making one of those leaps per day, then you'll go from 3000 emails down to 20 in two weeks. That's pretty good. (Note: This isn't theory; this is exactly the process I used when going from 800 emails to zero over the span of about a week in Korea.)
3. Quarantine and letting things burn while you re-establish sanity: This is where you say, "Okay, I've got five areas in my life; all five of them are shaky; I'm going to let four of them burn entirely while I get the fifth handled." Or maybe you preserve two areas and let three burn.
This is hard to do psychologically, because it seems a lot like admitting defeat. But if you had five impact areas that are totally out of control and you're totally erratic in them, then getting one of the areas to very good and perfect has completely outsized benefits compared to shoveling sand in the ocean in all five.
In a noteworthy time when I was out of control on a lot of habits and felt overwhelmed, I made only a single goal that was sacred to be done every day: Go workout.
That was it. I said to myself, "If I lift weights and nothing else, today was a win." Guess what? I went from having a lot of psychologically losing days to having a lot of psychologically winning days... I then re-normalized another area into sanity, and very quickly I was back on top of everything.
I've found almost nothing else that's universally applicable, but the following situational methods might apply as well: Changing your values, changing your priorities, working smarter instead of harder, redefining the problem, or working better with teams/people/delegation. Any of those might be the answer for your particular situation, and are worth exploring and questioning on.
But definitely, the mix of triage/bankruptcy, manageable chunks, and quarantine/let-burn-while-reestablishing-sanity work very well to get things back under control.
Stop shoveling sand into the ocean; make a plan to get things back under control and execute it.