So sorry for your loss. It is hard to lose a loved one and we all cope in different ways. You may try to do some exercise, just getting going may help you get some of those feelings out. When my mother-in-law, who I was extremely close to, passed away I found that doing a kickboxing DVD was a great way to get some of the feelings out that I didn't want everyone to see. I even found myself crying while doing it sometimes. Also, like erika said this could be a tribute to your sister. I hope you can find some peace in this tough time.
Goals for 2014:
Complete Couch to 5K
Sign up for and complete a 5K
Plan at least 3 outings with the family that involve being active