If you allow other people to take advantage of you at the beginning of your relationship with them, they will continue to abuse this power and will take even further advantage of you in the future. It is simply put in a few words – “give people a little and they will take a lot”.
People become comfortable with the idea that you will be there for them in certain instances. The more comfortable they begin to feel, the more they will ask of you as your relationship with them progresses.
This of course isn’t true under all circumstances or conditions, however it is something that one must be aware of whether starting a romantic relationship, friendship or a business association. Draw the line, or it will be drawn for you.