A counsellor once gave me an excellent tip. When I said I was missing my Mum, he asked what it was about her that I missed (like a specific trait). I said that I missed her sillyness and having fun (we played a lot of games) and he asked me if there was anyone else in my life who did those things with me. It reminded me that my SIL (who was my best friend in high school) gave me the same fun, so he suggested spending more time with her to help fill that gap.

It completely helped. Not something you can 'cure', but you can take the sting out sometimes.