"If I can do it anybody can "
This is a hard one to translate as it has many nuances, however, 'but I am as a god whilst you are a worm' is the most common. Whichever way it goes, accepting the invitation will probably involve also accepting extended periods of suffering, as you have embarked on an outing which is more rite of passage than bike ride, and afterwards you will find yourself saying, "It wasn't too bad, after all, if I can do it...".
See also, "how hard can it be".