I an trying to get over a relationship with a married man. We were lovers for 13 years and managed to keep our relationship secret. He ended the relationship 4 months ago. Does anyone have advice on getting over a relationship and how to dull the pain and overcome the feelings of sadness and fear.

Hey I'm pretty much in the same shoes as you at the moment. It is not easy believe me.
First off you got to keep yourself occupied, focus on work and work hard while at work, hang out more with your mates.

Work on YOU, think of how you were before the relationship and what made YOU happy.
Spoil yourself, buy new things, things that you have wanted for yourself no matter what it is, make changes to yourself to make you realise that you have your own two feet that you stand on.

Here is a break up survival guide written by one of the members here at AMHD. It lists a lot of great tips to help get on with your life

https://www.askmehelpdesk.com/relationships/how-break-up-survive-101-use-you-wish-114179.html

13 years is a very long time and even though I'm glad its over I know your feelings of loss are great. You have a long hard road to travel so acceptance is first and building a life that you enjoy is at the heart of your mission right now. It is very important to not isolate yoursef and have good friends around you for support and love as you seek out who you are without him. As the others have said staying busy with work, or family and seeking out new things to do, will occupy your mind and time. It won't be easy at all, but take small steps and move forward with your life. Your not on a dead end street any longer, and the possibilities are unlimited as long as you strive for your own happiness. Love yourself, and appreciate yourself, and don't sit on the pity pot, dwelling on the past, and you will be fine in time. You are free to explore yourself and life. Do so at your own pace.