John 10:10 (AMP) 10 The thief comes only in order to steal and kill and destroy. I came that they may have and enjoy life, and have it in abundance (to the full, till it overflows).
Happiness and joy is something God wants for all of us but the Devil wants to steal our joy. A great habit to form is being happy. We are as happy as we make our mind up to be. We can choose our happiness and not base it on the events, people, or things in our lives. We have to make the decision that this is a day we will rejoice.
Every single person has problems and we cannot let those problems keep us from being happy. While we are maturing and changing through the trials of life we can still enjoy ourselves, even as imperfect as we are. We need to learn to laugh at ourselves when we make mistakes rather than be so serious about everything in life.
If you do not have the ‘happy personality’ it does not mean that you cannot change that.
Psalms 118:24 (AMP) 24 This is the day which the Lord has brought about; we will rejoice and be glad in it.