Valentino Rossi admitted staying motivated amid Ducati's current plight is a huge mental challenge, after crashing out of the Laguna Seca MotoGP race while running a disappointing eighth.
The seven-time champion has been off the pace in the dry all season, and was enduring another tough race in America prior to his late crash at the Corkscrew.
"It was a very difficult weekend, and it closed in the worst possible way with a crash that I didn't expect," Rossi told the official MotoGP website.
"I lost the front as soon as I touched the brake and for me it was a big surprise because I was going quite slowly. But all this weekend we have had some difficulty putting enough temperature in the front tyre, so the front tyre after 30 laps is brand new.
"It's a pity, especially because we have had this problem for a long time and we are not able to fix it."
With MotoGP now heading into a three-week break before the next race at Indianapolis, Rossi conceded that maintaining morale with podiums out of sight was tough.
"Very difficult first half of the season. Probably worse than last year, or more or less the same," he said.
"It's very difficult to keep concentration and to keep enough power - physically but also mentally - to stay concentrated when you understand that you can only fight for not very important positions.
"But we have at least eight races to do. Last year the second half was very bad, so we have to keep our concentration and try to do the maximum every weekend."
Rossi has yet to decide where he will ride in 2013, having been alternately linked with both a Ducati contract extension and a return to Yamaha. He said he hoped the summer hiatus would give him chance to think more clearly about his options.
"I will decide in the next weeks, probably before Indy, because I cannot think too much during the race weekends because my brain is not free. But I think in the next days and next weeks I will take my decision," he said.