This question asks for an essay, however, that is a personal task that we cannot provide here. Nevertheless, we can discuss some of the ideas related to this subject in order to provide guidance for your work.
These two quotes differ on the perspective they adopt when it comes to the question of certainty vs. doubt. The first quote states that it is important to have an absolute, unwavering certainty about things in order to achieve greatness. On the other hand, the second quote states that you should never be too certain of things, especially your own opinions.
I tend to agree with the second statement. I believe that doubt is generally more important than certainty. Certainty can sometimes be more action-oriented. However, this action is riskier when you are fully certain of your beliefs, because it does not prepare you for contingencies, or for the failure that might occur. Moreover, having doubt allows you to keep an open mind, and constantly improve your views and opinions as you acquire more knowledge. On the other hand, absolute certainty can make you stubborn, and this can mean that you fail to realize the potential positive contributions of others to your own thinking.