It follows the death yesterday morning of his 84-year-old grandfather Barney, who lived in Bathgate, following a heart attack.
Gallacher was set to fly home after hearing the news but was persuaded to play in the season-ending event by his grandmother.
"The decision (to stay] was made for me by my grandmother," he said. "She insisted on me staying, saying it was what my grandad would have wanted.
"He was one of my biggest supporters and followed me all over the place."
Gallacher, who is flying the Scottish flag along with Richie Ramsay in the elite 60-man field in Dubai, added: "My emotions are all over the place right now. Yet I suspect my gran is correct. Barney would have insisted on me playing. I will be playing for my grandad this week even though golf is the last thing on my mind right now. When something like this happens it puts golf into perspective and makes you realise there are many more important things in life.
"Losing my grandad is the worst possible ending to what had been such a great year."