Is it possible to be too obsessed and too confident in your team?

I won't mention my favorite team but I have said it before. I believe they will be national champs and I'm real excited about a great season. But what happens if they don't meet my expectations. I have lived through heartache in playoff losses before and at time it has taken a toll on me emotionally.But for only a short period of time, then I accepted things and moved on to thinking about other things. But just the fact that I let an athletic team affect my serenity just doestn't sound quite right.