Cool card. Mathematically similar to Emergency Cache.
You can play Take Heart in three different ways:
A: You find an action that's safe to fail and intentionally fail it, ideally an investigate action or something that wont bite you after failing it, in this case Take Heart comes out exactly one action superior in action economy to Emergency Cache, granting 2 resources + 2 cards for 1 action and 1 card rather than 3 resources for 1 card and 1 action. Note that many survivor builds favor cards over resources.
B: You play it on a "free" test you're content failing, this would most often be a treachery test, for example Rotting Remains. You need to be careful in this case but the "1 card = 2 cards & 2 resources" actionless trade is a very large tempo boost.
C: You play it on a test you intend to fail, in order to trigger a "Look what I found!"/Dumb Luck/Oops!. And here we have the kind of deck you absolutely should take Take Heart in, the kind where you're able to turn failed tests into greatly successful ones.
At this point you might be thinking "So, its a better Emergency Cache?", not quite. The Emergency Cache is always only an action away, minimal effort for a reasonable gain, Take Heart might actually get held up by gameplay circumstance, no "Look what I found!" to combo with, no risk-free actions on the map (perhaps due to risky token effects) and no treacheries that you don't mind failing (Remaining sanity too low, risky effects), maybe even no investigates you can reliably fail (not to mention the occasional accidental success (Damn you +1 token!!).
Regardless, the survivor faction can replace Emergency Cache or even supplement it with this economy option, suddenly the "scrounger" faction has become one of the most economically healthy factions in the game.