As we continue to talk about Joy I think it's interesting to see that Paul says "let your reasonableness be known to everyone." This speaks to the attitude of rejoicing. Your attitude determines your altitude.
Some translations use gentleness or graciousness. So with the three words we get a good picture of the attitude that comes from someone who is rejoicing. It truly is a state of mind that leads to actions or attitudes in our lives.
Think about the people in your life that are gentle, not that they are wimpy, but that they are able to have self control in how they treat others. These are the people you seek out. You know that they are going to be encouraging and helpful.
The same goes with graciousness. When you encounter someone who is gracious you know that they will extend grace to you, even when you fail or mess up. They seem to be ok with allowing you to be you and not expect you to be perfect.
Finally, reasonableness is something we all need in this world today. With so much of our world going off the deep end and being unreasonable, we just need people who seem to have some sense! When we are reasonable, we are the type of person that can get through life's difficulties without flipping out.
Put all this together and we have someone who can be joyful in all circumstances. When you are the kind of person that is reasonable, gracious, and gentle you will always have a following and be able to give the reason for you joy.