Honestly, I don't think you're playing Fire Emblem wrong restarting chapters. What I found alluring about the series is the threat of death, the tension I feel each turn, wondering if I'm doing something stupid. Even when I restart the chapter, the tension is still there. I played XCom differently because for me, the tension was different, stemming from the lack of resources rather than characters. Characters just became another resource for me and I had no problems accepting their defeat.