Afghanistan posted 284 after half-centuries from Rahmanullah Gurbaz and Ikram Alikhil, before bowling out England for 215 to claim just their second victory at a World Cup.
We're not too concerned, it's just a game that we've lost," Rashid told reporters.
"We know we've got tough competition coming up, but I'm confident we can play really well as a unit moving forward.
"You are going to have games where players are out of form but I do believe we've got the squad, we've got the team and we've got the mentality to still be hungry."
England, who face South Africa in Mumbai on Saturday, are fifth in the standings with one win from three matches.
Persons:
Arun Jaitley, England's Adil Rashid, Afghanistan's Mohammad Nabi, Rashid Khan, Andrew Boyers, Adil Rashid's, Rahmanullah, Ikram Alikhil, We're, it's, we've, Rashid, Aadi Nair, Peter Rutherford
Organizations:
Cricket, ICC Cricket, Rashid Khan REUTERS, England, New Zealand, Thomson
Locations:
England, Afghanistan, New Delhi, India, Africa, Mumbai, Bengaluru