It means spending all your time feeling sad about your life, instead of trying to do things that could make you feel better. To "wallow" literally means to indulge in something with the idea that it's helpful or makes you feel good, when in fact, it might not help you or benefit you.

"Well.... I have these parents... I am not good at studying... I am not healthy..... I am financially poor..... I am ugly, so I am an unlucky person, so I don't really even want to live and just don't want to do anything in my life. Why should I go through this? I'm so unhappy." ---> Is this wallowing in self-pity?

I agree with Christina. I just want to add to that... "Wallow" is what some animals do in mud - they roll around in it and enjoy it (for whatever reason). When someone "wallows", that could mean they are purposefully (perhaps joyfully?) rolling around in the "mud", not motivated to get out - even though they have the power to do so. "Self-Pity" is usually excessive focus on your own troubles and unhappiness - feeling very sorry for yourself - with THAT being your primary focus. Put these 2 together. Self pity is the MUD that you are wallowing in - and you are just not motivated to pick yourself up and get on with what you need to.... When someone says you are "wallowing in self-pity", most view that as an insult, because "feeling sorry for yourself" is often viewed as selfish (focus on one's self over others) and choosing to be helpless (the opposite of choosing strength for oneself) Hope this was helpful! :)

"Being negative" is too general a term here. It's more about spending a lot of time pondering thoughts around regret, grief, or shame about either things you (yourself) did, or things that happened to you. It's a time when you're not being productive or coping well with the hardships of life -- instead of pushing self-pitying thoughts out of your mind or overcoming those emotions that drag you down, you think about them and let them take control over your life. "Wallow in self-pity" means to indulge in sad, regretful feelings directed at yourself. It is a phrase mostly used by people who are annoyed at this practice.