Cultivating a mindful attitude to towards negative emotions has been shown to reduce depression, anxiety etc. in a variety of studies - Is Mindfulness Good Medicine? Cognitive Behavioral Therapies (CBT) have also shown great promise to alleviate anxiety and depression - Is cognitive-behavioral therapy more effective than other therapies? The CBT approach basically states that what we think we feel. So when you find yourself
... reacting to your arising defilements
You are using enormous amounts of unnecessary energy identifying with these emotions i.e. not being mindful. This is likely to lead to other negative emotions like depression which in its turn leads to negative thinking patterns which then cause more negative emotions. So in a very real sense you are falling into patterns that quite literally
... suck the energy out of you
The Buddha wisely recognized these truths that are now being verified in the laboratory. So this is very sage advice and I second it:
To make a strong commitment, you want to cultivate right effort by making a continuous effort, by hanging out with wise spiritual friends, by balancing energy with concentration and by not doing things that suck the energy out of you like reacting to your arising defilements, eating too much and getting lost in mental proliferation.
It may be of interest to note that in Buddhism the three main causes for all the other defilements are ignorance, attachment, and aversion which then lead to anxiety, fear, anger, jealousy, desire, depression, etc.