Adventures thrive on interactivity. Without it games become uninteresting. Imagine if you will a game in which every time you read a book then you die. The players will quickly heave their characters not read books anymore. Or imagine a game in which every NPC you meet in a dungeon backstabs you. The players will quickly no longer interact with NPC's. Entire realms of emergent play are shut down because every time a character does X then a bad thing happens. The players need some motivation to continue having their characters interact with the game world. In short, not everything in the adventure should be negative.
When writing an adventure it's important to remember that you are not challenging the players or the their characters. You're creating an environment in which something is going on, an environment that is oriented towards actual play without being simulationist. It's important for the environment to be neutral towards the characters; some things they interact with being positive and some things being negative. If the baddies can control the laser pillar then the players should be able to also. If the tree has poison fruit on it then it, or another tree, should also have some stat boosting fruit. The Evil Sword should also be usable by the good guys. It doesn't have to be consequence free, it doesn't have to easy, but it should be possible, or even probable with clever play, that the party can take advantage of the elements in the environment.
There's an obvious corollary with NPC interaction in the dungeon.