The Holy Spirit will only change the parts not of God, the selfish, sinful parts - and then only if we let Him.
You only have to look at the disciples to see the complete mixture of personalities Jesus chose!
Look also at all the various personalities throughout the Bible, the strengths and weaknesses shown.
Moses, Gideon,Jehoshaphat and others were all taught an important lesson that it is not through their strengths but through their weaknesses that God did His most powerful works.
He made us all different, we're not robots off a production line. God chose us the way we are and the amazing thing is that He uses our weaknesses as well as our strengths.
Don't make the mistake though of interpretting happy bubbly personalities as being more full of Joy!
Many a sad, breaking heart lies beneath a smile and a laugh!
A colleague of my husband turned up at our house for the first time a month ago and was such a comedian, he could be on the stage. He told me the next day that it was all a mask. I told him I knew that as I felt his heart and felt his loneliness and pain, he was stunned! no one had ever spoken to him like that before, I told him that God is more real than he would ever dare to believe.
True Joy from the Lord is not determined by how we feel or is it affected by troubles and trials, in fact we are told in James 1 to count our trials as joy - just look at Paul the Apostle, everything he went through, yet he had Joy from the Lord, Jesus endured the death on a cross because of the Joy that was before Him (Hebrews 12v2)
Joy is a fruit we grow and cultivate regardless of circumstances.
One thing God has really impressed on my heart is that 'The Joy of the Lord is your strength' and the enemy's role is to 'kill, steal and destroy' everything God has for us, if the enemy robs your Joy - he also has your strength.
Paul Washer told us at Moriah that he is a very serious character when it comes to the things of God and yet has been criticised by Christians for being so exuberant in his joyful playing with his children! as he said to us I am also a 100% father who enjoys my children!
Scripture tells us that our Heavenly Father joys over us with singing! How wonderful is that - God himself looks upon us with such joy that He sings!(Zephaniah 3v17)
Jesus was 100% human as well as 100% God - sure he feels every emotion as we do - as He wept and grieved at losses He sure would have also laughed and shared fun as well.
He would have had to have had a personality like that to attract all the children He did!
I'm sure the disciples would not have had a fully somber and serious three years with him - there must have been times of joy and laughter!
And one day He will present us to His Father, pure and blameless - with much Joy! (Jude 24)
Scripture speaks of a celebration in heaven eveytime a sinner repents! it's a very joyful, noisy, happy place!Jesus taught the parable of the prodigal son to express our Fathers great Joy over His child who returns home -much music and dancing, so much so the elder brother was jealous, he'd never had such a party thrown in his honour!Luke 15v22-32
Sure Jesus would have always looked you in the eye,He was a great communicator with a heart of compassion - I think the question is could we look Him in the eye!
Don't worry about your personality, how serious you may be, or how exuberant and bubbly, unsaved people will see Jesus in your personality as you grow close to Lord and grow in the fruit of the Spirit, especially Love - 'by your love people will know that you are my disciples'
My husband had to sign a contract that he will not promote or preach his faith at work - the thing is, it has made no difference, he's not had to try and promote his faith, people have asked him if he is a Christian because of the way he acts and how different he is.
He is regarded a father figure to his team mates and even his boss and is held in the highest esteem, we've even had his colleagues turning up on our doorstep to talk with us and he's never had to volunteer talk about God! - it's all come from them.
It is by your fruit you will be known but don't strive at it, trying too hard will turn people away from you, just allow God to do the work in you.