Sealed bids means that if you get it you will never know how your bid compared to others, except that it was the highest. As long as your bid is what you can afford and what it is worth to you, you aren't overpaying.
I agree with MoneyCat: if this is your lifetime home, go for it. I paid full (high) asking price for my current home 12 years ago, but 1) I could afford it - just, 2) nothing like it has come on the market in this area since, and 3) I wake up happy to be here every day, and it is my "lifetime" house. I would have regretted not buying it much more than I would have missed the money in my bank account.