Steer clear of anything adverse. If it's adverse, it's working against you — like adverse weather conditions or the adverse effects of eating too much sugar.
Coming from the Latin adversus meaning "turned against," adverse is an adjective describing a factor that seems to work against or actively harm something. Think of the related word, adversary, which means enemy or opponent, so that if something is adverse, it acts as if it were the enemy. Often you can find expressions such as "he is risk adverse" as a way to say that someone doesn't like taking risks.