Since I meditate (and follow a mindfulness training) I have much more vision in my thoughts and feelings. I am a long-time worrier and of course you can not change it from one day to the next. But the fact that I now understand my thoughts and feelings makes you aware of the fact that you can make a choice. A few times a day I scan my emotions and discover how I feel at that moment. I agree that you can now behave differently to feel different. But I also want to give the tip sometimes to lay down your feelings and just experience it as it is. Just discover how you feel without attaching a label to it whether you want to feel it or not. Gloomy emotions are also part of our lives and do not arise for nothing.