The most important thing to remember with a personal statement is that it is your chance to tell the tutors why you want to study this subject. Extra curriculars are useful for demonstrating to them that you have motivation to learn more about the subject beyond what you may be studying already in your coursework, but just listing off all the volunteering and work experience you are doing isn't going to get you a place. You need to contextualise these experiences, what drew you to do it, what did you get out of it, what did it inspire you to do next...? The tutors want to know about the learning journey that you are on because going to university is about guided self study and they really want to see if you are capable of doing that. If you think about what you have done and how you are going to write about it then I think that you probably already have plenty to be talking about. Just make it personal, talk about how you felt, but keep it focussed and to the point.