Anxiety About Loved Ones Dying (specific scenario)

I feel like my brain doesnt know how to function without creating SOME form of anxiety. I just got over an incredibly lengthy and stressful event in my life that created a HUGE amount of anxiety in my life (this event lasted 6 months) Yesterday was the first day since the event ended and it should have been a massive relief but now my brain has shifted to stress and worry and anxiety about people I care about dying.. More specifically my boyfriend is going mountain climbing by himself (not like rock climbing, but hiking up a very large mountain) this coming August and I am worried he is going to die. I realise this is SO far in advance. He has done this for years (this will be our first summer together)...he is from the mountains so it is 'in him' so to speak. Hiking up a mountain allows him to re-charge...its like his meditation. We are going back to his home town in the summer and that is when he will do it. He will be gone all day, by himself with no cell service. He does go prepared, he trains for months, maps out his route, he has been doing this for over a decade, he knows what he is doing and people do this ALL of the time, yet I worry that he wont come back this time. Im just worried he will hurt himself, or that he will run into a dangerour animal, or something equally as bad will happen. Asking him not to go would not be fair, and I would never do that because I know how much he loves going.

I have no idea how to not worry about this. I shouldnt worry about it at all to this extent, and I DEFINITELY shouldnt worry this far in advance. I jsut picture myself that day, which I will spend with his Mom doing one thing or another, and I can already feel that anxiety that I know I will feel all day that day...constantly checking my phone for a text from him saying he is done and on his way back.

I can;t talk about this specific worry with anyone...I find it embarassing...its only January. I feel like I Should be able to get a handle on my anxiety and stop worrying but I cant.