Complaining never made anything better. Everyone has things in their lives that they wish were different (or better). But simply complaining for complaining’s sake doesn’t bring change. That’s whining. (Venting is different and should be done judiciously and with intention.)
Complaining brings down the mood of everyone in the conversation – especially the complainer.
If there is something that you can do about the situation, then do it. If nothing can be done, then change your thoughts about the situation.
If the situation warrants you bringing it up, think about what is the best way to say it. Consider whether affirmation or some other strategy will work instead of complaining.
If you are tempted to complain, first express appreciation in some way – no matter how small it may seem. Then, use positive words to propose a realistic solution to the situation.