Even the closest of workmates can disappear from your life once you are out of the workplace and not seeing each other on a daily basis.
If you tend to socialise mainly with people that you work with, start thinking about the people you want to continue to have a relationship with and think about the ways in which you could do that.
I think it's worth pointing out that, if you want to remain in contact with colleagues and friends from work, you need to be prepared to do most of the work involved in staying in touch yourself - even if it feels like you're the only one making the phone calls and suggesting the meet-ups. Life moves on and, even though people start off with the best intentions of keeping in touch, it doesn't always work out that way.
Tip: If you would like to read all the blog posts in this series that have been published to date, scroll down to the 'Categories' section in the left hand column and click on the 50 things I learned about retirement category.