Have you tried mindfulness? It's not something I'm an expert on but it really helps connect you to the moment and stop fears of what the future holds or getting tied up with past disappointments.

When I look back, the truly happy memories have all been about a single moment. A time when I felt connected and wasn't worrying about things ending but just enjoying things being. Most of the people I was with have now gone from my life but I enjoyed their company while they were here. And I try to be mindful of the fact that lots of long term relationships are far from happy all the time so this idea that we have to keep people with us forever doesn't hold up and can actually lead to insecurities, possessiveness and unhappiness. Allow the right people to stay with you for as long as they want and try to accept that if they leave, it's their choice and if that happens, feel sad then and not now.

It must be the weather today because this isn't the sort of advice I usually give or am able to follow myself. But right now I believe it's the only way to be truly happy .