Saying "anything good happens through grace and anything bad happens through karma", keeps you grounded.
When someone blames you, they take away some negative karma from you. If you understand this, you will only feel happy about it.
When you praise someone, you take on their good Karma. When you blame someone, you take on their bad Karma.
When you increase your sense of knowingness, your Karma gets reduced. For example, you feel like throttling somebody, but because you are aware, you don't do it.
It's your desire or attachment that causes tiredness, not the work. Karma Yoga is acting 100% even though you aren't attached
Until the impression of your previously done Karma is on your mind, that Karma manages to exist. You are freed from Karma once the impression is erased.
You deal with the situation. All that you face in life are result of your Karma. It could be latent or present karma.
Every impression is Karma, but there is nothing to worry about because Karma is not like an engraving on a rock – it is fluid. And Karma is always bound by time because every action has only a limited reaction – it is not infinite.
Everyone’s karma affect everyone else. Don’t worry too much. Keep doing good and that will uplift you.