You should consider theoretical physics when you have a strong math intuition, if you like thinking in abstract terms about physical systems, if you get thrilled when you find a new mathematical approach to describe a physical problem, and if you like the unknown, get motivated by intellectual challenges, and want to understand 'god's mind'.
A lot of your time will go into translating your math into numerical algorithms, whatever time is left you will spend on writing publications, and in technical discussions with colleagues. The remainder is time for real contemplation.
More than often you will discover, after weeks or months of hard work, that the route you chose was bound for failure, and that you could have known this in advance. As soon as you come to such insight, you know you are growing into your field of research. You start all over again, and you do so with the optimism that one day you will solve the problem. Your strong desire to understand 'how the universe works' keeps you motivated.
And yes, you will start drinking lots of black coffee, and you will struggle for years to get a tenure position. Once you have such a position, you discover that your former class mates who grasped only 10% of the math and physics you fully understood, but who went for an engineering study, earn twice as much than you. Yet, you don't regret for a second the career choice you made.
If these prospects appeal to you: go for it!