Fire Emblem is a difficult series, I don't know if you guys have heard

[Oyvoyvoyv]

Just be careful about the info you get before the fight.

 

Enemy level

Enemy type (and thus weapon).

 

If enemy level is higher than yours, be careful. Don't hesitate to retreat.

If the enemy's weapon "beats yours" (axes beat lances, lances > swords, swords > lances, and light > dark, Dark > anima, Anima > light), be prepared to retreat.