It is easier to go downhill than to climb uphill, so it is easier to fall into bad habits than into good ones.
Bad habits don't come suddenly. They come little by little without your knowing their danger. Schoolboys first pick up little bad habits from schoolmates. If they see bigger boys smoking, they also want to learn to smoke. If they see their friends gambling(赌博), they want to gamble.
When they get older, the habits become stronger and stronger so that they can no longer get rid of(戒掉) them. From copying, they learn to steal. From gambling, they learn to cheat. At last, they become distrusted(不信任的) by everybody. How necessary it is that we get rid of the bad habits in the beginning!