I haven't experienced this sort of thing for a number of years - but I used to experience it alot.
The following may (or may not) apply to your particular situation but I'll share it anyway because someone may find it useful. :)
I think these sorts of negative bursts of emotion happen during a time of transition in your life.
During these times, you sense glimpses of another world for yourself where you can experience joy, power and abundance but you are still living a physical reality where those things do not yet dominate your attention.
So you get reminded occasionally of where you are, rather than where you are heading, perhaps at a subliminal level, and it can knock you back a bit when you notice the difference.
And because your sensitivity is on the increase, it can feel more painful to look at where you are than it used to when it was your habitual thought pattern.
I think the solution is not to get too involved in where the feeling came from - because you'll just eventually drag yourself back there - but rather to keep bringing yourself back again to focusing on the joyous life ahead of you and all the good things you have in your life right now - even if you have to do that again, and again, and again...
Eventually, you will reach a tipping point where everything suddenly changes and these kinds of feelings just become things of the past and, even if they do recur, they will seem so alien to your new joyous life experience that they will fade as quickly as they arise without any conscious effort on your part.