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In front of an England record crowd of 45,619 in their first game at the new Wembley, Sampson's side were beaten by three first-half goals.
"The objective of the fixture was to be better as group of people and players," Sampson told BBC Radio 5 live.
"We learned a lot of lessons of what we need to do to be competitive with these teams in the summer at the World Cup."
England conceded in the sixth minute when Alex Scott put into her own net, before Germany striker Celia Sasic scored twice.
"It was difficult at half-time to come in at 3-0 down," Sampson added.
"It was a tough decision whether to shut up shop and keep it respectable or keep trying to play and take the initiative. The attitude in the second half was outstanding.
"We learned a lot of lessons of what we need to do to be competitive with these teams in the summer at the World Cup."
England, who booked their place at next summer's World Cup in Canada with a 100% record in the qualifiers, have reached the last eight of each of the three tournaments they have played in.
Captain Karen Carney, who won her 100th cap against Germany, told BBC Sport: "It wasn't what we wanted, but we have six months to get it right now.
"If someone said get it right now or in six months we would take it in six months. They are a strong team.
"We were a bit naive in the first half, mainly in the first 20 minutes. We have to be better, go away and come back, fitter, faster, stronger."
Coach Mark Sampson believes England learned lessons from the 3-0 defeat by two-time world champions Germany.