Choose a big problem, stand up for a cause, or set high goals for yourself and dedicate yourself to them.
Most of us avoid problems, set achievable goals, and are fence-sitters for the causes that affect us. This may help us lead a good life, but it cannot make us feel great.
To lead a great life you need to pick up a big problem, set impossible goals for yourself, stand up for a difficult cause, and work towards achieving them. The bigger the problem you choose, the more difficult the cause you stand up for, or the more impossible the goals you set yourself, the greater would be your life. Look at everyone who you think is leading a great life and notice the problems, causes or goals that they have dedicated themselves to. Mahatma Gandhi picked up the problem of India's independence. Martin Luther King picked up the cause of racial discrimination, and Alexander set himself the goal of conquering the world.
It is your life. Be satisfied with a good life, or choose to lead a great life.