Karma, as defined by Wikipedia "is energy of thoughts, words, & actions. Karma is the term used to describe the cycle of cause and effect. A culmination of all a person is doing, done, or will do. According to the theory of Karma, what happens to a person happens because they caused it with their actions. Karma makes a person responsible for their own life & how they treat others. The conquest of Karma lies in intelligent action and unemotional response."
Karma is like baggage from your past, present, and future. Sanchita Karma - sum of past karma to be resolved in this life. Prarabdha Karma - portion of sanchita experienced in this life. Kriya Mana Karma - karma being created, to bear fruit in the future.
Life's lessons are for our benefit, teaching us what we need to learn before moving foreward. When interacting with others it is vitally important we do not create more karma for ourselves unintentionally. This might happen by contributing energy to a situation when we should be silent and understand that we may be helping someone through their own karmic journey.
Realationships, work experiences, and states of mind can all be karmic, these episodes in life are designed to help us through our personal karmic journey. Our existence might be explained as a time to learn and improve our karma by knowing when and how to respond in every situation to invoke positive change.
Some tips for making the karmic journey:
Be unaffected by others actions.