You can't help ageing, but you can help how you deal with it and feel about it!
I'm nearly 62, so I do understand how you feel. At this age my mum was diagnosed with cancer, which went on to kill her, aged only 66. So I'm very aware of the need to live my life.
The best advice I can give you is to try and make every moment count.
If you don't like the grey hair, get it dyed. I have my hair, eyebrows and eyelashes done regularly! I know that some women look stunning when they go grey, but I don't. I look worn out and tired. Similarly when I have my eyebrows and lashes done I look much more 'present' and vital.
Make sure you're eating well and that you're keeping yourself fit. That doesn't mean you have to be a gym bunny, but make sure you're not starting to slump into/onto the sofa all the time (very, very easy, especially in lockdown)
Try not to worry about things like insomnia. The more you worry about it, the more likely you are to suffer from it. I always thought that when I retired, the insomnia might recede - but sadly no! However, at least I know I don't have to get up to go to work, so if I'm awake in the middle of the night it's no problem. I get up and go and read my book for an hour or so.
Do you work? Do you have plans for your retirement? Best advice I can give you here is to make sure you have something you will enjoy doing when you're not working - whether it's gardening, golf, fitness, learning a new language, DIY etc. Something that will occupy your time but also your brain.
Try and switch your perspective so that you view the next decades as a time for you - once you're no longer working, your time is your own and no-one has any call on you. It's hugely liberating.