I can't say that I had a physical aversion to converting, but I did have a very serious psycho-spiritual attack about 2 weeks after my chrismation in December 1992. I was doing evening prayers and suffered a severe panic attack, with a total focus of the attack on my doubts about my faith, not only as an Orthodox Christian, but whether I even truly believed in God. I ended up clinically depressed and suffering from round-the-clock anxiety and panic attacks all over whether I really was a believer. Some good meds, and a lot of talking with my priest and a psychiatrist brought me out of it within a couple of months. It was probably one of the worst periods of my life, following right after the most joyful. I knew to expect some kind of post-conversion difficulties or let down, but I wasn't expecting this kind of spiritual attack.
I'd known I had a family tendency towards towards anxiety and panic attacks, but I had a lot of triggers at that time including job stress, the purchase of a new house, the big emotions of conversion, and I truly believe, demonic attack. Ironic that I have less doubts about the demonic than God himself!
The phrase that I hung on to from my priest was "Lack of faith is not doubt, but indifference". Almost 20 years later I realize that for me faith is a conscious choice. I'm not going to have carefree, childlike faith. I choose to believe even though I am always going to have doubts. That doesn't make me an unbeliever, just someone who struggles with belief.