I read some where that you need to something for 30 days to make it your habit so if you want to change something in your personality you practice it for 30 day and you will have that new habit.
I always sleeps more then needed even after a lot sleep I don’t feel refreshed. So I make a promise to myself that I will fix my time of sleep I will sleep at 1 pm at night and wake up at 7:30 am. I did that for 30 day. After 30 days I wake up at 7:29 am without even alarm going off. And my energy level has also gone up due to this. I still feel a little at time of waking up that 5 more minutes won’t hurt. But as time passes by it is becoming easy to do it.
You can use the same method on personality developed also
First decide what you want to change
Only select one thing because we have limited amount of will power everyday
Do the thing for 30 days without any breaks as I did with sleep time
You will start getting result very soon as one thing become easy to do you should get to other habit that you want to improve as now your old habit has changed. By this method you will be able to develop a good personality.