When you have a perfect salary in mind, you probably tie that desire to things you want in your life. Regardless of your reasons, US News argues you should leave your personal finances out of negotiations because it hurts your case.
Unfortunately, it doesn't matter if you can't pay your mortgage, need to save for your child's education or want a new car. Your compensation is based on the value you provide to your employer, not your finances. If you feel compelled to tell your sad story, don't. Make sure to leave the personal issues out. Instead, try describing the immense potential you have to bring value to the company. You don't want to engender pity or despair, but rather inspire excitement and confidence. Because potential is not guaranteed, it may seem counterintuitive, but "that uncertainty can lead people to think more deeply about the person they're evaluating - and the more intensive processing that requires can lead to generating more and better reasons why the person is a good choice," [Daniel] Pink writes in his book. Make it easy for them to feel good, not guilty.
Personally, I've been on all sides of this argument. While I think it's sound advice, I've both failed and succeeded by following it. I've also said "I need $X to live the way I want to live, so I can't take the job if my salary is below that number" and gotten more than I asked for. So while that's nothing but anecdotal evidence, I think you need to consider the best argument for a given situation and the person you're negotiating with. In larger companies, you'll do better by playing to your strengths and avoiding any kind of guilt trip. With smaller groups, you may serve yourself better with a simple and honest statement of the facts.
3 Colossal Salary Negotiation Don'ts [US News]
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