Stuart Lancaster's revamped side maintained the progress they began in this year's Six Nations with three battling displays in their Test matches against the Springboks but still lost the series 2-0.
Haskell, who made an impressive international return in Saturday's battling 14-14 draw in Port Elizabeth, feels he knows the areas the team needs to work on.
The 27-year-old flanker said: "To draw or win against a southern hemisphere side is pretty special, especially on their own turf.
"Moving towards the autumn internationals, hopefully this has been a big step, but I think we have got to be a bit more creative in attack. We have got to test teams a bit more.
"We have got the physicality and the ability to finish. We have just got to be a bit smarter, get the likes of (Chris) Ashton and Manu (Tuilagi) running through holes rather than at people."
England will play the Springboks again during their autumn international programme later this year, as well as facing Australia, New Zealand and Fiji.
Haskell expects the current group of relatively inexperienced players to grow into a tougher unit.
"In terms of culture and character, this has helped as well," said Haskell, who by the autumn will be back in the English game with London Wasps after spells in Japan and New Zealand.
"You can look back and say that in the heat of the battle, in the fire of Port Elizabeth, we came together and we didn't take a backward step.
"We didn't have the polish we wanted but we were certainly positive.
"Every time you take to the field you gain a bit more knowledge about what it takes to win in international rugby.
"I think we will be a bit more settled. To push South Africa like we did in all these games, we have got to be pretty positive about that."
Haskell did not play in the Six Nations due to his commitments abroad and had to bide his time after being called into Lancaster's 42-man touring squad.
He sat out the first two Tests but a chance to return arose because of injury to captain Chris Robshaw and he showed he has lost none of his passion for international rugby.
He said: "When you are in the system and loving life you take it for granted a bit.
"But when you are on the other side of the world and have been written off, and when you get that chance to pull on the England shirt again, you don't want to leave anything out there."
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