Most buyers need to lose at least one house in order to buy one because they haven't fully committed to the purchase. The loss may be due to not seeing enough homes - attitude of it needs work so i am not paying a penny over... - taking too long to negotiate and getting trumped by anther offer.
no one has regretted getting the house, but they have regretted losing the house.
Negotiating too hard (more than 3 rounds) can upset a seller, so much so i have seen sellers sell it for less just to piss off the first buyer. Only time can soften a seller but the risk is losing the house to an other buyer.
Quantifying all the reasons not to buy the house, like it needs work, is a lot easier than quantifying how well the house will serve ones needs. Perspective needs to be balanced to make reasonable offer otherwise the offer will go no where.
"I am in not a rush" is not a reason to not buy a house when you are ready to buy a house or to not pay a fair market price for a home. Its all based on comps. Comps dictate fair price.
When there is another offer and the seller gives you bottom line, pay the bottom line.
Losing a house over a little money is silly becaue 1) time invested to get to this point 2) time it will take to continue looking 3) somehting better may be a long way off