Fend means to provide and look out for oneself without any help from any other person. It means you do not have to rely on other people to help you provide your needs. When a child is growing up and under the care of parents, it is normal for that child to look up to parents fo provision of certain basic needs such as food, shelter, clothing, and education.
However, when a child reaches a certain age; in some places eighteen or twenty-one in other places, that child has grown into adulthood and is old enough to begin to do to certain things on their own which includes fending for themselves.
If you are old and healthy enough to fend for yourself, you should do so. Depending on other people to provide for you will only cripple you for life. It is wise to make efforts to fend for yourself because you would end up being independent and not be at the mercy of others.