Hi. There is a Buddha's thought that says: 'Even your worst enemy can not hurt you as much as your own thoughts'
That thought reaffirms the doubt without evidence.
we spend imagining and that makes us doubt what we can achieve and we do not want to leave it to God to decide.
I am not saying that there is nothing to do, it is to make the request believing that they will be achieved by previous study and so we trust.