Lost capital is just the same as a product in bad state that can't pass quality control. When you have one, you don't try to recover the money lost on the product. You only try to make this products in bad state the minimun of all the production, reducing them into the minimun we can for avoiding bigger outcomes.
The same for forex. You don't have to recover it. You have to make losses the minimun you can and next trying to maintain those losses into minimun and incomes to the maximum. You only can learn about problems and trying to avoid them, not trying to recover all.