He claimed First Minister Carwyn Jones was saying "I told you so" while Plaid Cymru was using the poll's outcome as an "excuse" to call for independence.
Labour and Plaid had a "little Britain mentality" when a "globally facing Britain" was needed, Mr Davies wrote.
He made the comments in an article for The Times newspaper's website.
On Thursday, Welsh Government economic advisor Kevin Gardiner said some people were "perhaps unduly pessimistic" after the vote to leave the EU.
Within hours of the Brexit result being announced on June 24, Mr Jones said he feared it would cost Wales jobs.
In his article, to be published on Friday, Mr Davies said the first minister had been "particularly vociferous in his doom-laden economic forecasting, and in denigrating those who chose to leave".
"He has closed the doors on cross-party negotiation and now, having lost his nerve, seems unable to negotiate a deal for Wales, resorting instead to finger-wagging and pronouncements of 'I told you so'," Mr Davies wrote.
Plaid Cymru's call for independence "betrays how out of kilter they are with the needs of Welsh communities", he added.
"The prophets of doom and the independence mongers alike are wrong to take such a warped view of referendum result."
Mr Davies urged his political opponents to "lift their eyes to the sky and consider the limitless potential that now lies ahead of us and to embrace the outcome".
He added: "Instead they seem intent on clinging to a little Britain mentality. A globally facing Britain is what is now needed."

Natural Energy Wyre Ltd said the Duchy of Lancaster has given it an exclusivity deal to create the UK's first tidal energy power station.
If approved, it will be built on the Wyre estuary, which belongs to the Queen in her role as Duke of Lancaster.
The Royal Society for the Protection of Birds said it had concerns about how the scheme could affect wildlife.
Natural Energy Wyre Ltd said it now needed to find £10m to proceed with a formal planning application.
It said the power station would support the government's renewal energy objectives, create thousands of jobs and attract 600,000 visitors to the region, as well as help with flood defences.
A barrage, which would span the mouth of the river with six turbines, would take three years to build, the firm said.
It will produce renewable energy four times a day, on the turn of the tide, for more than 100 years, Natural Energy Wyre Ltd added.
Graeme Chalk, head of project management for the Duchy of Lancaster, said the tidal barrage would "provide a source of green and affordable energy for many years to come".
Tim Melling, RSPB senior conservation officer, said: "Climate change is the biggest threat to the natural environment so it's vital we invest more in renewable energy. But tidal barrages are not the right option and this proposed scheme on the Wyre would cause major damage to the estuary.
"A barrage would knock the tidal system out of sync and destroy this prime feeding habitat by reducing the size of the feeding areas and making them available for less time."
"Prophets of doom" and "independence mongers" are taking a "warped view" of the Brexit vote, Welsh Conservative leader Andrew RT Davies has said.
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Plans to build a £200m tidal barrage in Lancashire that will power tens of thousands of homes have been announced.