Lukaku managed little more than an hour all season for Italian side Napoli, but has played almost twice as many minutes at the tournament for Belgium, who topped Group G to set up a Round of 32 clash with Senegal on Wednesday.
"I'm just happy to be here because, if you look at my season and how it went, normally I should never have been at the World Cup," he told reporters on Monday.
"So for me, being here, playing, helping my team, making a difference, being decisive in a match - it's great. So yeah, like they say in English, 'go with the flow.'"
The 33-year-old striker understandably looks short of full fitness, but has a goal and an assist in 121 minutes and been especially effective off the bench.
In Belgium's first game against Egypt, they were trailing 1-0 and looked bereft of ideas until the introduction of Lukaku forced an equalising own goal around 20 seconds later.
Lukaku started and played over an hour in a 0-0 stalemate with Iran, then had another instant impact against New Zealand, scoring a goal shortly after coming on to put Belgium top of the group once more.
"I have plenty of time to analyse where the spaces are and then I just try to be able to slip in or do a bit more," he said.
"I think that when you look at it as a substitute, you really have to pay attention together with the other players sitting with you on the bench."
Lukaku is one of the last of Belgium's golden generation - coach Rudi Garcia's "oldies" - still with a chance to deliver on their promise, though he called on his teammates to ignore the outside noise and focus on difficult opponents in Senegal.
"Technically they are very good, tactically they are very strong, physically they can make the difference, so for us it will be a big challenge intensity-wise," Lukaku said.
"I said in the dressing room it will be 50-50, so let's see what the game brings."
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