Why is it so hard to talk to an ex-boyfriend or ex-girlfriend?

It depends on what kind of experiences have defined you during your relationship, and the relationship itself. It is also about the manner in which the breakup had taken place. Our brain has the tendency to associate the positive experiences with the negative ones, which happened after the positive experiences but are intertwined with them, which of course, makes it harder to enjoy solely the positive experiences. In order to do that, I propose separating the experiences and viewing them as individual remote ones, while looking at the relationship as a joint of lessons, growth, and shared emotions which is specific to this relationship because each person is unique, logically 2 people will create an unique bond. This is my complete opinion on it.

It's hard to talk to your ex perhaps because nothing can change the fact that you have created some memories together that may remind you of your past. Sometimes there is this fear of falling for them again which you may not want to. Some people also believe that talking to their exes could make it hard for them to move on. Apart from that, in some cases if there the break up was due to some arguments or misunderstanding, you may also be afraid to hurt the other person's feeling and end up suppressing your emotions. You may also think that they may not like you anymore or your text would antagonize them. It's definitely not an easy task to not to talk to someone with whom you once had a very special bond.

It can be very difficult to speak to an ex, because you have so much history between the two of you and things have changed so much. You might be confused about what your "label" is, or perhaps even jealous if they have been with other partners.

Because they are your ex fro a reason. Whatever the reason may be it is still a reason. If it was a bad 1 then its better for you to keep away.

it is hard due to the fact that this person used to be in love with you and either isn't or things aren't the same anymore. things change , people change , love changes.

I believe it is hard to talk to them because you closed off a really strong bond with them. It can feel really awkward or scary, since you might be afraid that you weren't good enough and what they have now is better.

Because they might still have feelings for you or they could be in another relationship. Some people want to forgive and forget

Mainly because you both have so much history that talking to them especially immediately after a break up can be a painful reminder of what both of you have lost.

You had a past filled with good and bad memories. When you see someone that you've made memories or have spent so much time with it's hard to ignore.

I think it depends on the nature of your relationship before you got together and how the relationship ended. Messy breakups tend to leave things in an awkward state. I have found that my partners that ended on mutual terms and who were my friends first have been the easiest to talk to afterwards because there are no hard feelings and we had a foundation of friendship built before it developed into a relationship.