Sadness is an emotion we cannot deny or avoid because it creeps in when life takes an unexpected turn. Pretending not to be sad doesn't take the sadness away, rather it only leads to resentment, hurt and regret. The best is to face it heads on by practicing mindfulness like those ones you listed. Among them is taking a walk in nature and one would feel the calmness in them making them enlightened and see a new ray of hope.