Know your enemy
Ever wondered what the colored squares are when you first start playing the Adventure maps? You can look at it as a rough guide for how much damage you give or take in a certain map, which gives a good approximation of the difficulty.
These guides by LagunaLevine have the maps in question while the colored squares are still present:
Adventure
http://www.junkiesnation.com/2014/09/26/hyrule-warriors-adventure-mode-map-guide/
Master Quest
http://www.junkiesnation.com/2014/10/27/hyrule-warriors-master-quest-adventure-guide/
TP
http://www.gamerheadlines.com/2014/11/hyrule-warriors-dlc-twilight-adventure-mode-map-guide/
In order from easiest to hardest, the order is:
Green < Yellow < Purple < Orange < Blue < Red
Here's my assessment for Twilight Map colors, since TP is notorious for having really scaled-up enemy stats:
Green and Yellow: Easy!
Purple: Moderate, if you've gone through most of the first Adventure you can handle it.
Orange: The enemies start doing a lot of damage for the 10-heart requirement, and some of these have tricky Damage Taken requirements. At least the enemies aren't too tanky, so you shouldn't run into problems finishing in time... unless you have to kill The Imprisoned, which does show up in a couple of them.
Blue: Some of the worst missions are here. The damage taken is very high for the 10-heart requirement, and Gold Aura commanders can really stall out your ability to complete the map in time.
Red: Actually, at 25 hearts the Damage Taken Requirement is pretty reasonable... except for the maps where half the enemies are glowing red/yellow. You can expect really tanky enemies here, too. While most maps seem to be possible below Level 100 and not using power-up potions, I'm not sure if that holds true for Ganondorf's red tile missions.
So yeah, if you want to know what to expect for damage, or you just want to avoid the bizarre side of the Twilight map, those color-coded maps help.