Flashbacks will happen, my mom has only been gone a year and a half and sometimes I get them too. They're hard, and it's almost like they take you back to THAT day and you feel like you are grieving all over again. Some days are harder than others.

Try going for a walk, clearing your head. Find something to help the time pass, do something in honor of your mom's life, go out with a friend, to lunch, to the movies, find a new place to have an adventure, get immersed in a new book, etc. Hope my suggestions help.... I find if I keep myself busy, I don't have time to think about sad things. It's just how I am able to get through my day easier.