"Wish" must be treated carefully. When you cast it, a djinni appears and offers you a few things you can choose from, like "all allies fully healed" or "regain my used spells". The outcome really depends on the wisdom of the caster - the wiser you are, the more chance you have that the text of the options offered are exact and can be interpreted in only one way, and that's important!
E.g. a wizard with low wisdom might get a choice like "I want to be more powerful than enyone" and the djinni will say "OK, I'll give you the chance to improve yourself" and will summon a horde of enemies on him! If you're wiser, the same wish would be "I'd like to be stronger for the duration of the battle" and the djinni will raise your strength points.
Even with high wisdom you may get tricky choices, so choose wisely. Usually noble desires like healing will be fulfilled.
