Mindfulness is a type of meditation in which you focus on being intensely aware of what you're sensing and feeling in the moment, without judgment or interpretation.
Practicing mindfulness involves breathing methods, guided imagery, and other practices to relax the body and mind and help reduce stress.
Meditation is like any other skill or activity, the more you do, the better and more you can do. Keep it simple, don't stress about something that is suppose to relieve stress. Five minutes is fine, better than no minutes.