A tight, restricted chest means that we have tension and stress held within our body. Our body and our minds are linked, so a tight chest means anxiety in the mind whether you acknowledge it or not.
The solution is to counteract that so that you improve your posture, feel good and loosen up so that you open up and are more relaxed, comfortable and confident.
An easy way to open up your chest in less than 2 minutes is to do a couple of exercises 20 -30 times each quickly whilst breathing. All you need to do is have your arms and shoulder height and pull them back and forth 20 to 30 times and have two different hand positions. Eg thumbs pointed back or thumbs pointed forward.
If you do these stretches daily they will improve the quality of your life as better posture, physiologically speaking will increase your self belief.