Khawaja spent two years out of the Australian team, and in his return at Lord's he played a sloppy shot to get out in the first innings before making a fighting 54 in the second.
But the 26-year-old said he needed to be stricter on himself and not accept 50s and 60s as good scores.
Khawaja is looking to cement his place at No.3, a position that sums up Australia's failings over the past few years.
Shaun Marsh in Sri Lanka 2011, is the only Australian No.3 out of eight candidates to have scored a hundred since Ricky Ponting moved from the pivotal first-drop position in 2011.
Khawaja knows he needs to be the next.
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"I played five games last year of Shield cricket for Queensland. I scored a hundred and a couple of 80s. I missed a few hundreds. So I probably wasn't hard enough on myself personally," Khawaja said.
"I can't speak for other players. I know it frustrates me to hell getting 50s and 60s.
"You do all the hard work and it's probably the best time to bat.
"Obviously it's up to the individual in terms of batting and trying to go big. Putting that onus on themselves.
"Ever since I got dropped from Australia a couple of years ago it's been up and down, trying to find my way back. I feel like I'm in a good place now. Hopefully I can make some of those starts into big scores."
However, Khawaja admitted that in many ways, there's no quick fix for Australia.
While England boast 628 caps between them, Australia share just 298.
Khawaja doesn't believe the Sheffield Shield competition is a factor in poor performance, but says you can't buy experience.
"There's been a lot of nice performances over the last couple of years. It probably hasn't been as consistent or everyone doing it at the same time," he said.
"We've got a young side. I think eventually you'll find players finding their feet.
"I think the (Shield) schedule was alright last year and I think it's getting better this year. I've got no complaints about it."Khawaja replaced Ed Cowan in the line-up for the Lord's Test and will get another chance to spend time in the middle in Australia's three-day tour match against Sussex starting on Friday.