Rav Arush discusses how people get depressed because even though they try their best to succeed, they fail and continue to fall. He writes that if someone gets depressed, he should realize that he doesn't have enough Emunah, because he thinks that he could accomplish something that Hashem didn't want him to accomplish. The biggest proof that Hashem didn't want him to accomplish it, is that he continues to fail!
Even though a person tries his best, often Hashem doesn't let him succeed because he hasn't yet built up the "vessels" to be able to correctly react to success (as Hashem's doing). Succeeding under such circumstances would lead a person to haughtiness, and this is worse then any sin since it severs a person's relationship with Hashem.
If a person keeps on doing T'shuva and Davening for divine assistance, eventually he will build strong enough vessels for him to succeed at what he is trying to accomplish, and when he does finally succeed, he won't attribute his success to himself but only to Hashem.
Therefore, the only Bechira (free-choice) we really have is whether to be happy or not, irrespective of our success or failure.
Success doesn't breed happiness, but happiness breeds success. Even if we keep on losing our long drawn out battles, as long as we recognize that Hashem is the one pulling the strings, we can be happy since Hashem ultimately knows what is best for our Tikkun.