Please accept my deepest sympathies for your and your mum's terrible loss. There are no words that can make you feel any better but please know that, in time, you both will begin to heal. I'm sure your dad would want you to remember him with happy tears instead of sad tears. Try not to dwell on the loss, just try to remember all the good times you were blessed with because of him. Please take care of yourself and your mum. Sending prayers and hugs for your entire family. I am so sorry.
