* TSX down 40.98 points, or 0.33 percent, at 12,457.90 * Rona down more than 10 pct as Lowe's walks away from bid * Energy stocks limit losses as crude steadies By Alastair Sharp TORONTO, Sept 17 (Reuters) - Canada's main stock index fell on Monday, hurt by a drop in home improvement retailer Rona Inc after a potential suitor walked away and fading investor euphoria over last week's aggressive move by the U.S. Federal Reserve to spur growth. Rona fell more than 10 percent to C$11.47 after Lowe's Cos Inc withdrew its C$1.8 billion ($1.86 billion) bid for the Quebec-based company. The sharp sell-off in Rona was one of the heaviest weights on the Toronto Stock Exchange's S&P/TSX composite index , which was down 40.98 points, or 0.33 percent, at 12,457.90 by 10:20 a.m. (1420 GMT). The index's fall followed several strong sessions of gains late last week on the back of the U.S. Federal Reserve's fresh round of monetary stimulus. The index hit a five-month high on Friday. "It's just some sober reassessment of last week's events, no more, no less," said John Ing, president of Maison Placements Canada. "With oil strong there is interest (in energy stocks) and banks are benefiting from the likelihood of low interest rates to stay until infinity," he added. A 0.45 percent rise in Canadian energy stocks played the biggest role of any sector in preventing the index from falling further. Major producer and refiner Suncor Energy Inc gained 0.9 percent to C$34.63, while smaller Crescent Point Energy Corp added 2.2 percent to C$43.01 as the price of crude steadied after days of gains. After starting stronger, the country's biggest banks and insurers turned negative, with Manulife Financial Corp down 1.3 percent at C$12.46 and Royal Bank of Canada off 0.4 percent at C$55.87. Barrick Gold Corp and Teck Resources Ltd were among the heaviest weights, down 1 percent to C$40.76 and off 2.1 percent at C$32.30 respectively, after moving up strongly last week.