I agree with Honey. The grieving process can be long and hard, and even when you think you are handling things really well your emotions will slip up on you. Your concentration is gone, your energy is low, highs and lows are magnified. I lost my Mom and a beloved 6 yr old grandson in a 10 month period and still have times when I am overwhelmed with loss and loneliness for the two of them. Don't beat yourself up, do what you can, when you can, and if you have to, put it aside for a while and work on something simpler, or smaller or maybe even something that is memorial to your sister. Good Luck.