An individuals boundaries will change over time. A person will not not have the same set of boundaries for every relationship. The type of boundaries you have within yourself towards another person depends on the dynamic of that relationship. For example you can have very clear boundaries with a friend but with another friend you may find it difficult to assert yourself.
Having good boundaries does not mean you are selfish or cold. Being able to say no to someone is an act of setting a boundary. Saying no is really important as it shows that you are able to take your own opinions into consideration.