Karma Yoga is described as “performing of worldly duties with an attitude of detachment.” While Raja Yoga has more of an ultimate goal (samadhi), Karma Yoga believes that the journey is the destination. The path to working hard and helping others is the path where you find your samadhi. There is no actual destination.
In fact, if you have a destination, you are practicing Karma Yoga incorrectly. Human instinct is to work for the sake of achieving something. If that something is attained, we feel happy, and if it is not attained, we feel sad. Our emotions take over us either way, and we feel happiness or sadness from the achievement, not the process of achieving. Work is considered a mundane process. We go to work not for the everyday experience of sitting in an office, but for the monthly salary we get in return.
While that may be instinctive, it is not right. You should obtain benefits from the process of helping others, not from the end-goal. There should be no end-goal. You work for the sake of working, and help for the sake of helping—not to achieve something specific. That is the philosophy of Karma Yoga.