Everyone has the ability to increase resilience to stress. It requires hard work and dedication, but over time, you can equip yourself to handle whatever life throws your way without adverse effects to your health. Training your brain to manage stress won't just affect the quality of your life, but perhaps even the length of it.
Grief is never something you get over. You don't wake up one morning and say, 'I've conquered that; now I'm moving on.' It's something that walks beside you every day. And if you can learn how to manage it and honour the person that you miss, you can take something that is incredibly sad and have some form of positivity.