There are lots of times, during our life that we have to make decisions. Which school we go? Where we should live? What kind of policy our company should have? Should we decide all alone or we should make decision with others? I agree with this statement that "A person should never make an important decision alone".
When you make a decision alone all of consequences is one you. If all your assumptions do not go well, you have all responsibilities. It makes lots of pressure on you. For example you have to decide where your family goes for summer vacation. If you decide alone and then you find out that the country you choose is not as good as you think, other family members see you responsible. You are worried all the time when you make a decision alone. Despite that, if you decide with all family members about the destination and other things the trip, the responsibilities are for all. If they do not enjoy the trip, they do not blame one person because all of them were involved of the process of making decision.
Another reason is that, when you get help from others to make a decision, they will help you to see other aspect of the every decision you make. For example or with y you want to choose your major in university. You do not have information that what kind of job you will do? Or how will your ordinary work be in the future of choosing the major. I mean a person who had the same major with you can give you a clear picture of future then you can understand if you want to choose that major or not. In some cases that you have to make final decision yourself it would be very helpful to at least hearing other's ideas than just yourself.
In conclusion, I think making decision with other people participation's or help is better than making it alone.