So I want to start by sharing my thoughts and experience, but would really like you guys to chime in too, because I'm sure I'm not going to think about everything!
(And no I'm not being cheeky/arrogant, I may have top streak now but it hasn't been always the case and I'm sure as hell it's not going to be the case forever so I'm really encouraging people to post up, it's not a high-streaks-only club, it's whatever folks find helpful to push past their former streaks! 
).So I think there are 4 main types of losses in the DERP (not counting stuff that's outside the game, like server connectivity or computer crashes):
1. Getting trapped (i.e. either starting clogged, or getting blocked by level mechanics / plants).
2. Running out of resources / not being able to tank a hit from the boss (i.e. Bleaty, maybe Aequitas).
3. Misclicking (for example, accidental double-click (i.e. targeting a monster with a spell and then getting a "free" attack on top); accidental click somewhere, i.e. instead of clicking that L1 Golem, you click the L9 Illusion just next to it; radial menu i.e. pressing the button just a tad bit too long somewhere and getting a bonus attack, etc.).
4. Brainfreeze (not noticing retaliate; forgetting that Gorgons have petrification; forgetting your slow strike; etc.)
So what can be done about each of these? I think some ideas are:
1. To reduce risk of getting trapped:
* Cherish glyphs that can open up ways, or allow you to tap into unaccessible blackspace, like: ENDISWAL, PISORF, WEYTWUT; LEMMISI, BLUDTUPOWA; and to a certain degree, WONAFYT.
* Consider taking the "Extra Glyph" preparation to increase the odds of finding more of these glyphs (and avoid "Fewer Glyphs" for the same reason).
* Deities that offer some of these glyphs - JJ, Binlor - are usually (but not always) safe preparations in a Daily.
* Glowing Guardian's "Absolution" boon is a non-intuitive but nevertheless effective way to remove some of the low-level monsters that can block paths
* Avoid using IMAWAL unless you also have ENDISWAL (or are absolutely, completely sure what you're doing).
* Likewise, avoid The Earthmother. She is an awesome all-purpose deity, but she does tend to clog the map. Again, she can be used completely safely, but it takes a lot of skill, so unless you want to keep a notepad ready for counting how many plants are "out there", just ignore her if you can.
* Familiarize yourself with the workings of the tricky maps that can trap you: most notably Shifting Passages and The Labyrinth; but getting over-cursed in Cursed Oasis can also spell doom. Also, some maps are more clogged than others (Ick Swamp, anyone?).
2. To reduce the risk of running out of resources:
* Make sure you're "in shape", so to speak. Skill with Desktop Dungeons is partly academic, but partly just being in practice. If you just play one Daily per day, you're going to experience a bit of skill decay, and you'll be more prone to losing some of the trickier runs. I advise being in good enough shape to regularly win Vicious, it may sound overkill but due to RNG, some Normal/Hard Dailies are actually harder to win than some average Vicious runs! Rule of thumb: play one extra game each day on top of the Daily (ideally, Vicious and/or VT).
* Check the spoilers before playing to see if there's anything specific to the map. The boss, the layout, the high-level monsters may need you to adjust your strategy. This is especially useful for Goat runs, or to a lesser degree to Gorgons/Vampires/Chemists/Rats.
* Make sure you have some experience playing non-standard combinations. Like, Rats with Bear Mace are proven awesome, but in most Rat dailies until today, there wasn't any knockback. So knowing how to win reliably without KB is very useful.
* Also make sure you're familiar with the easy-to-craft combos. A Mystera Gnome, for example, is almost always enough to win.
3. To reduce the number of misclicks:
* Turn off Radial Menu;
* Switch to right-button attack;
* Play slower to reduce twitching.
* Look for ways to get Death Protection. CYDSTEPP is a keeper; Namtar's Ward is an auto-prep; Badge of Honour is an auto-buy-and-pop.
4. To reduce impact of brainfreeze:
* Pause for a moment before clicking to see if the death warning lights up, and stop to think why if it does;
* Pay special attention to - or if possible, avoid altogether - game elements that introduce extra drawbacks. For example, slow strike (platemail/really big sword); avatar's codex; patches!!.
* Keep your brain and body well-nourished; don't have too much alcohol, caffeine or hallucinogenic drugs in your system when you play; if you're feeling depressed or anxious or too tired, you may try to think some happy thoughts before attempting the Daily; if you're in a bad shape emotionally or physically (flu, moonhate, or whatever), try to go for a safe-but-sure "plan B" approach to just getting the map over with without dying. When I felt skittish, I went for a smoke before playing... now, I quit smoking since then (I think), but I can still take a quick pause, pour a glass of water for myself, and just generally do trivial things for a minute or two, to boost my self-confidence. I mean, it's just a game, and streaks come and go, but it still feels a bit bad to lose one when it happens...
Yes?
