At the moment, I may not be the best resource on means of dealing with life when it becomes overwhelming, as I've been failing pretty miserably at navigating those very waters recently. However, it's not without reason.
When I have been more successful at getting through overwhelming times, I seem to employ a host of strategies and activities, depending on where I am and of what I'm capable. A late night drive always mellows me out and offers perspective, thanks to the dearth of traffic and the moments I can peek at what stars are available for viewing when I'm stopped at a light. Time spent in natural environments and/or hiking and walking works wonders for me, when I can get to or do them. Productivity seems to ameliorate negativity and stress in me, but that can sometimes backfire. A simple treat can buy me a little time, at least to think, as I drink that overpriced cup or coffee or nibble on some candy. Plus, that last one is just fun.

Hanging out with my friend who lives close by helps at times too, as she laughs fairly easily and tolerates my eccentricities...well, most of 'em. Talking is the best strategy of all for me, if you can call it that. An empathetic, willing ear is so helpful and appreciated when I'm overwhelmed.
Hope this helps, or is even slightly interesting.

Thank you for a great question, Fresia!