Inward spiritual conflict - healthy or unhealthy?

Does awareness of spiritual conflict within you lead you to despair? Does constant need to do battle with tendencies to sin cause you to doubt the genuineness of your Christian faith?

Bishop J. C. Ryle helps us to see that these experiences, far from being signs of ill spiritual health, are in fact vital signs of spiritual life! 

Sanctification … does not prevent a man having a great deal of inward spiritual conflict. By conflict I mean a struggle within the heart between the old nature and the new, the flesh and the spirit, which are to be found together in every believer (Gal 5:17). A deep sense of that struggle, and a vast amount of mental discomfort from it, are no proof that a man is not sanctified. Nay, rather, I believe they are healthy symptoms of our condition, and prove that we are not dead, but alive.

Quoted from J.C. Ryle, in Holiness (EP Books). Cited by A. Hoekema in Saved by Grace (Eerdmans).