It is difficult for a number of reasons - it can feel physically clumsy, it can be a bit embarrassing, it can be boring!! Etc -- but it is REALLY important thing to do.
So - do it at parkrun. You can always find somebody slower than you at parkrun - so check them out and deliberately run with them. Have a good chat with them as you go along. BUT - they will hate you for this because you will be running at a comfortable conversational running pace whereas they will not. They will struggle to converse with you - but at least, at the finish, you will be able to gee them up in the last bit and get them to run a PB ( which they will appreciate ) Win-win!!