Yea sure have. I spent around 7 years of intense study in apologetics and theology. I was on the battleground constantly, engaging in this debate and that, preaching, teaching, serving always. I was worn out, I was beginning to war after the flesh, then if that wasn't bad enough I wasn't receiving fresh empowerment and rest from the Spirit of God.
I became so focused on those topics and engaged in defending the faith I didn't defend myself with mental rest, easy biblical feedings and walking in joy with my Lord. So after a while, I was depressed, sad, worn out and dead inside. I was saved, loved and knew God...no doubts, but spiritually I needed a getaway and God provided me one. So for almost two years, I put down the vast majority of theological and apologetical works, left all discussion groups, stopped debating altogether, left off writing on my blogs, and shut down myself.
That was a really good thing God had me do. I was able to recoup, refresh, get back in spiritual shape, renew my passion, find new heart and life in my endeavors for the Lord.
Maybe this is not exactly you, but I do know the true sense of deadness and emptiness of spirit...even when I was obedient to what God had me do...be encouraged to shut down anything that's draining you.
Make it very simple on yourself. Bible feedings that minister life and power to your soul, prayers, and worship that allow you to re-enter the presence of God with genuine authenticity, cries for help and renewal.
Take leave from the battlefront for a while. Engage only those times you know the Spirit is granting permission.
Do not go back into the battlefront until you are well and you know it.
hope this helps.