What are the most important factors that negatively affect decision-making?

Anger, fear and commitment plays an important role in negative decision making.

Anger augments a sense of personal control, lowers perceptions of risk, and makes people less willing to admit a mistake. As a result, angry employees are more likely to commit further resources to a failing project or choice. By contrast, fear makes people second-guess themselves and often abandon support for efforts that have gone even slightly off the tracks.

By paying close attention to the emotional tendencies of their subordinates, managers may be able to predict or even influence whether their employees will escalate their commitment to a problematic plan or decision, or whether they will give up too soon. In some cases, bosses may need to advocate for emotion-control training, which can reduce the amount of fear or anger specific employees demonstrate.

Bottom Line: Emotions can get in the way of rational decision making. Anger, in particular, can make employees increase their commitment to a failing plan. Managers who understand these tendencies can help lessen their effects on the organization.

It is also connected to not allowing all members of staff engage in the decision making process as a result it brings strife among some who are entitles and less favoured ones.

Barriers grow along with disrespect and dis-content, dis-satisfied employees among the business.  The effect of a negative feeling affect the decision hence making it negative.