If during negotiations you seem overly eager or show your hand too soon, guess what, the terms can change. Impatience can give the other side the upper hand, which usually makes it harder to strike a deal. Impatience can force you to pay a hefty price — position, profits, etc. etc. etc.
Waiting can be harder than moving forward, and it sure takes more discipline. One has to learn to control his/her emotions… which isn’t easy. But when the terms are right, stand firm, be strong, and don’t give in. Try to get better terms, but if you can’t, walk away or wait :-).