45 is still not old, as they say, life starts at 40. So continue living your life and don't limit yourself. Enjoy your life, don't worry about tomorrow; focus on what you can do now. Keep fighting. And it's not necessarily a bad thing to lose friends. True friends, no matter what, will not abandon you in times of difficulty or joy. However, if your friends are not contributing positively to your life or well-being, it's not wrong to distance yourself from them. People who bring stress and add to our problems can truly affect our lives negatively.
Not sure if life starts at 40 now - I think that was more when people had children earlier, so by 40, they were nearing adulthood and the parents had far more freedom, energy, and a bit of money.