If you are not offended by Christian doctrine, you can turn to St. Paul's letter to the Corinthians [1 Corinthians 12:31-13:8a] in which he defines love.  The same rules that apply to love, pretty much apply to maturity--one comes out of oneself in his/her thoughts and actions.

Love is patient, love is kind

It is not jealous, is not pompous

It is not inflated, it is not rude;

 

I think you are better off coming up with a definition of maturity.  It can be defined biologically, such as when a being achieves certain physical characteristics.  It can be defined sociologically, such as when a person achieves certain rites of passage or responsibilities.  It can also be define personally, in terms of what it means to you.  You need to choose how you will define it.

Maturity, as a process, implies change and growth. Maturity is sometimes seen as a state of being, a kind of personal-behavioral product or end-point, but we can also see maturity as being defined by growth, change, and a deepening of experience. 

When writing three paragraphs on maturity, you may want to touch on the idea that maturity has multiple definitions and select one of those definitions as your focus. 

Maturity is a term which holds connotative meaning. Wat this means is that the definition for maturity changes with each individual based upon the emotional definition the person holds for it. This is different than a denotative meaning (which is found in the dictionary). While beginning with the denotative meaning for a word is a great start, the connotative meaning must follow--given this is what makes your meaning true for you.

To begin, I would suggest providing the denotative (or dictionary) meaning of the word maturity. After than, you could do a couple things. First you could compare and contrast what it means to be mature and immature. Some words can be defined based upon its difference from another. After that, you could provide ideas for what it is not. For example, maturity is not having a "temper tantrum" if one does not get their way. Lastly, the term could be defined using other similar words, ideas, or concepts. This defines the word by showing its similarity to other words, ideas, or concepts.