Perhaps rather than impatience, you may wish to use the trait of impetuosity, which better implies the character trait of reckless and rash irrational actions since impatience can sometimes not lead to action. Then, for a motivator to begin the introduction, you could cite the passage of Act II Scene 6 in which Friar Laurence counsels Romeo against rushing into marriage: "These violent delights have violent ends...." For, this passage expresses the theme of what you have chosen to write about.
While enotes editors do not write for students, we may make suggestions for you. So, in your thesis you may wish to state that the impetuous natures of Romeo and of Juliet--their "violent delights"-- cause them to make rash decisions and to interpret the cause of their actions sometimes as fate (rather than their own responsibility) and to react in an irrational way to these occurrences. Certainly, there are many examples that you can pull from the play as support for such a thesis.