How to Stop Complaining and Be More Positive?

How does one stop complaining about every little thing? I'm usually the person to tell others to look on the more positive side of things. However, ever since my depression has worsened, all I do is complain about basically anything whether it's a big deal or not really anything that I need complain about. I'm super negative and bitter and feel like everything will turn out the worst in the end and I really want to learn how to not think like that, even if there is something bad going on. And I'm not saying that complaining or venting is anything to be ashamed of, almost everyone complains at least once in a while, but I complain numerous times everyday to people that probably don't need to hear all that negativity, including myself. Any advice would truly be appreciated! Or if you simply relate, feel free to comment 💕