Some of the teachings I have had the good fortune to receive refer to the "wisdom of 'no big deal'."
It's simple, really.
As humans, we often make an awful lot out of things that don't really amount to all that much. We get into patterns of repetitive thought. It's our nature. It's nothing about which to feel bad about ourselves. It's just what we do. We worry about what might happen in the future and try to cope with it, but we create something known to some as an "anxiety gap." This means that since the problem, as we perceive it, is actually not real—it's something we are imagining in our minds; therefore, we cannot actually deal with it because it isn't reality. The problem doesn't actually exist at this time.
We also make a big deal out of things that make us happy or cause us pain. The Dalai Lama once gave a wedding present to a young couple, and this is what he did. He put his hand on the head of the bride and said, "Pain is not a punishment. Pleasure is not a reward. They are just ordinary occurrences." Then he did the same for the groom. Then he just kept repeating the word, "Kindness. Kindness. Kindness." This was his gift to them.
Pema Chödrön's spiritual teacher, Trungpa Rinpoche (he was her teacher for many, many years until his death some years ago, but she refers to him and what she learned from him quite frequently in her own teachings) used to say, "No big deal..." to her when she came to him to tell him about situations that made her angry or fearful... OR when she came to him to tell him of great insights or wonderful experiences. It was like his way of saying that one shouldn't get attached to pleasure or pain. They are two sides of the same coin, and we tend to get attached to both. It is wise to recognize when we are getting attached, and remind ourselves to say, "No big deal!"
I hope this is making some sense...
I think saying, "No big deal" is also a way to accept things the way they are and to surrender to the reality of the present moment.
May you be able to relax and say to yourself, "No big deal," when it would serve you to do so.
Peace and Namaste.