In defining your own strengths and weaknesses, use tools such as the StrengthsFinder, a personal SWOT analysis, Myers-Briggs or personal motivational assessment to uncover more about your real self.
Alternatively, start with a simple list.
What do you like most about yourself?
What needs to change?
Explore your current attitudes, assumptions, behaviors and habits.
Also, ask for feedforward from family, friends, colleagues, your boss, even people who may not like you, explaining that you want their opinion on your strengths and weaknesses, so that you can work on these. And then ask yourself: is it easier to change perceptions or to spend energy building up something that is not a strength?