Each life aspiration has its own fears and wants. When you have a want and you achieve it you get points added to your aspiration score. Of course, if you aspire to have a family and your spouse dies then that is a fear that has been realized and you immediately lose aspiration points.
There are six levels on your aspiration meter: the highest level is platinum, the next level is gold, and there are two levels of green and two levels of red. If your character has a meter filled up to the platinum level the meter is considered fulfilled and your character will be more willing to do tasks that they normally don’t like to do. Make sure that your character's aspiration meter does not reach the red levels because they will go through a nervous breakdown and that requires the attention of a psychiatrist which will automatically appear.
It is important to maintain a high aspiration score because it will determine how your character will live once it reaches the life stage of an elder. If your character grows up well with a high aspiration throughout each life stage you will see that when your character dies the gravestone or jar of ashes will be better looking.