In yoga we practice mindfulness and self-awareness. We seek to maintain clarity in our everyday activities so that we don't get swept away by emotion or wrong-thinking; so that we can make wiser, kinder choices; and so that we can be honest with ourselves about why we have behaved in certain ways. If we understand what lead us to shout at that person/eat or drink too much/ignore our needs, then when we are in that situation again, we can make a more prudent and positive choice about how we react to it. In this way, gradually and with regular practice, we get to live happier, calmer, healthier lives.
Yogis do this by making time to reflect every day. It's as simple as being quiet and being still. It is very difficult to hide from yourself when you are being very still and very quiet (that's why so many of us spend so much time being noisy and rushing around).
This practice doesn't make you free of anxiety, pain, grief, jealousy, fear or frustration - these things are all part of being human; we can't live without them any more than we could live without love, joy, serenity, hope or amusement. It gives you the capacity for self-awareness; the ability to stand slightly aside from your emotions and to observe yourself honestly and clearly in any given situation; it's the gift of perspective... You notice an emotion; you feel it; you watch where it came from and how it manifests itself in you; and a natural pause finds its way into your life; the pause before you act. That pause is the difference between flying off the handle and being able to explain yourself lucidly; it's the difference between noticing the source of your jealousy and allowing it to consume you; it's that pause that allows you to be the best version of yourself, instead of the one that gets the same thing wrong, over and over again.