The minute you settle for less than you deserve you get even less than you settled for

"The minute you settle for less than you deserve, you get even less than you settled for."

Any specific moments come to your mind?

Do you still get angry with yourself that you had agreed to conditions lower than requested (and your gut was screaming "Don't!")?

How was your motivation level?
How was the other side's appreciation/respect level?

Stop underselling yourself. It does not serve anyone.

Make it your priority to find out (and know) how much you are worth on the market and be ready to say 'NO' if the negotiation leads nowhere.