Even if it's just in your head, it's a dangerous habit. You've been taught (by centuries old systems of power and privilege) to be angry without action. You've been socialized to believe that you can't do anything to change the things in your life that you don't like. You've been trained to believe that your happiness depends on forces outside of yourself.
Clearly, this training does not serve you. So you can let it go.
The truth is: You are responsible for everything around you. Your life is YOUR life. The people, places, and things that surround you are not just reflections of you — they ARE you. Complaining obscures the truth of this reality. Complaining is taking the easy way out. By complaining, you denounce your responsibility to do the difficult work of transforming the experiences that cause you suffering. Instead, you point fingers. You slander. You blame. You name all the ways everyone and everything (except you) need to change.
If you delude yourself into believing the things and people around you are not YOUR responsibility — you risk missing out on opportunities to cultivate a life of extraordinary purpose. You give up your power. You relinquish your role as the captain of your life's ship, and become merely a passenger.
The truth is: You are SO powerful, and your words and thoughts are powerful causes. Pay attention to them, and be careful. If you notice yourself complaining, stop and consider exactly what you are manifesting. Ask yourself, "What am I conjuring with these thoughts, these words, this energy?
If you find yourself stuck in a place of hopelessness about a situation or experience — if you hear yourself thinking, "This person, this thing, this experience will NEVER change," know that YOU are an active participant in making that true.
Let me be clear: No one is telling you not to be angry or annoyed at things that are fucked up and worthy of frustration. Quite the opposite. Be mad! Feel all of your feelings! You have every single right to feel and express your dissatisfaction. But you can't stay there. Let your dissatisfaction inform your action plan. Let complaints be valuable information, and nothing more. If you don't like something, DO something about it. Complaint without action is evidence that you have either forgotten (or are afraid to use) your magic. It's fear of taking responsibility for your own life. Let it go, let it go, let it go, beloved.
This life is too precious and too sacred and too fleeting. Make it into what you want.