AT 250kmh, there is not much room for error.
Ash Walsh was painfully reminded of the lesson in his V8 Supercar debut at the Sandown 500 on Sunday.
For 33 laps, the Yamanto racer's dream debut looked like it would be realised.
After qualifying 22nd fastest, Walsh had got his and Tim Blanchard's Dick Johnson Racing Falcon into 15th spot.
It was then one lapse of judgement cost him dearly. "I was a little bit close to the Erebus car," Walsh said.
"He broke earlier than I expected.
"I jumped on the brake and locked the front right tyre and from there I was a passenger."
Walsh hit the wall and his and Blanchard's race was over.
"I should have been a little bit more over-cautious," Walsh said yesterday from Melbourne where he is taking a couple of days rest and relaxation after a big weekend.
"Up until that point I was going really well. I'd moved forward seven positions and had good speed."
Walsh was scheduled to drive another 40 laps or so, then hand over to Blanchard, when disaster hit.
"It was going better than I expected," Walsh said.
"I thought I could get through on five but had passed seven and was still going forward.
"Our pace was pretty much the same as the leaders except for (winner) Paul Dumbrell. It was going exactly how I wanted it."
Walsh was distraught after the incident, not only because it ended his own hopes but also that of his co-driver and team.
His teammates and bosses were supportive of him but left him in no doubt that it is not to happen again.
"They were okay," Walsh said.
"They said it happens, learn from your mistake and don't do it again."
Walsh turns his thoughts to the Bathurst 1000 from October 10-13 where he hopes to put his valuable experience from the weekend into practice.