Should I fast on this Mahashivratri?

Please give me honest and factual answers. Been a Lord Shiva bhakt since a kid, just like my father. Mahashivratri is the only festival i celebrated from the bottom of my heart and fasted each year happily. But I lost my father at a young age at the most unexpected way. I left everything related to the religion. This Mahashivratri will be the first without him physically. Honestly don't feel like fasting so because I don't care anymore but I had a thought how my behaviour affects my dear father? Why should I fast this year and how will it affect him? Please tell me what the religion says. And how as his daughter, I do good deeds and go the right way which don't affect him. Is there any connection?