to me, the subtext could be something in the direction of telling us to value things that we have taken for granted, this navel gazing action is kinda like someone who's contemplating the deeper meaning of life. "It is a good opportunity to say, This world is really awful! But I have intestines! " Now the function of intestines is to extract nutrition from the slimy goo that we have eating, so to me this sentence kinda means "It is a good opportunity to say, This world is really awful! But I have intestines, so that i can get the good stuff out of it. well, this is just my interpretation, hope it helps, :-)

I think the writer was trying to be humorous. You probably already know that "navel" means belly button (which my dictionary says is 肚脐眼 in Chinese) and "gaze" means to look at something for a long time. However, when you put those two words together, the idiom "navel-gazing" has a totally different meaning. Merriam-Webster defines it as "the activity of thinking too much or too deeply about yourself, your experiences, your feelings, etc." or "useless or excessive self-contemplation." You can say that navel-gazing is when you have a problem but instead of taking action to solve it, you just think and think and think about it. Anyway, when the writer in your example talks about navel gazing, he is taking the term way too literally as though it means "to look at your stomach for a long time." This is supposed to be humorous and I guess it will be funny to some people! I hope that helps!

长袜子皮皮: As DancingBear indicates, there is a good deal of confusion in that person's message. The author of those remarks clearly has a "flippant" attitude, and what was written is not to be taken very seriously.---Warm Regards

I think so too, but still can't figure out what exactly does that word stand for, maybe because of lack of context?

I think the writer of that letter was high on something.