Bumping into your ex

As I was casually chatting away to a friend, she mentioned that she had awkwardly bumped into an ex and didn't quite know how to act in the situation. It got me thiking about that age old question of whether you can actually ever go back to being friends with someone after you have split up with them. I myself have never been in this situation. I have only ever had the one boyfriend and I am still currently with him. I have never been into relationships. I have never seen the advantages of being attached to a single person and I thoroughly enjoyed being the single girl in my group of friends. I'm not saying that I didn't enjoy the male company, of course I did, but I just never found someone that hooked me, until I met him.
I'd known my boyfriend since I was 11 years old. We used to sit by eachother in Science and History and he was always so sweet. The strange this is, we were only ever friends. Well, actually, that's a fib. He did give me a valentines card when I was 12 but I was so shy that I wouldn't accept it. Poor thing! Anyway, our friendship grew and grew and we became very close. We would confide in eachother about little things like homework worries, but also in more serious things such as family illnesses. He became the one person I could rely on for anything. He would pick me up from work, take me for coffee to cheer me up and phone me if I was down. It wasn't until I turned 17, that I realised that I was in love with him. Due to our closeness as friends, I always put it off because I didn't want to ruin everything. We spent our last year in sixth form on and off but never cemented the relationship status. We went on holiday to Magaluf with a group of friends and even though we spent most of our time alone together, we both still came home single. It wasn't until the second week of Freshers that we finally became a couple. We were on a night out when I happened to walk passed him with another girl. Now, he was clearly in his right to do so, he was single after all, but it completely broke my heart and I realised that I could never see him with another girl again. So, I took the plunge and told him how I felt. That was two years ago exactly and we are still together.
I never want to go through the experience of having to see him as anything other than my boyfriend and I can't imagine ever splitting.
No matter how much we argue and ignore each other, I could never actually end it and become friends again. I simply wouldn't be able to stop myself from treating him like my boyfriend.
That's the big debate. What happens when you split up with someone and he is still in your circle of friends? How can you go into a room and not instantly hold his hand or give him a kiss on the cheek? After spending a lot of time with someone, I don't see how you can just change your way of acting around them. Obviously, that relationship would have ended for a reason and so maybe you don't have those feelings for that person anymore but what if it had to end for reasons that were out of your hands like long distance or work, could you still act like just friends? Or would those old urges come back to you?
I suppose, if you do want to continue your friendship with an ex then this is just something you have to deal with. You have to put aside any old feelings and just go back to the very start. The beginning. The easy ground where everything is simple and safe.
I suppose the only reason why I am seeing the back to friends scenario as difficult is because I can't imagine every being like that with my boyfriend. I guess I'm just lucky to have found him and to never want to let him go. He was an amazing friend and an even better boyfriend so luckily for me, I will never find myself in this awkward situation. 

Mia xx