If you have to say anything, make sure it's something nice. It's really easy to moan complain and criticize but it's far harder to always find something nice to say to someone or about a situation. Saying something nice is much harder because it's natural for us to moan and criticize.
If someone asks how your weekend went it's much more natural to start with the bad weather than it is to talk about the great time you had and the wonderful company you were with. When you are asked how you are getting on at work, the things that spring to your mind first are the things that annoy you most, and how much boring work you have, and not the good things you are doing.
Believe it or not no matter how horrible someone is there is always something good about them, and your job is to find the good bit, talk about it to others, draw attention to it and highlight it as much as you can. This is the same as any problematic situation you are faced with. Look at any problem situation as an adventure and consider it a challenge you have to face rather than something to get you down.
Whenever you are asked for you opinion about something, somewhere or even someone, say something positive and flattering. There is loads of research that tells us that being positive has its benefits, especially that people will gravitate towards you without knowing why. The positive aura around you acts like a magnet and attracts people closer. People prefer being around upbeat, positive, happy and confident individuals.
When you only say positive things about people, it cuts out all the negative stuff and stops you from gossiping, telling tales and complaining about other people.
Before you speak, pause and try to find something good to say. Try doing this for 10 days, says something good every time you talk about something or someone.
Try it you'll be very surprised how good it feels and after 10 days you won't stop. Don't just believe me, give it a go and see how much better it makes you feel and how much more positive people see you.