This reaction can make you doubt your victory, but what's really happening is that old, deep conditioned patterns are coming to the surface as "I" and "me" and "mine" and making a bid for your consent or acquiescence that these kleshas are in fact "I" or "me" or "mine."
This self-assertion of old, conditioned patterns can be so strong that you can almost feel like there's another person trying to assert him/herself as you. Or, it can feel like dark malevolent external forces fighting against your progress. Don't buy it! It's all your mind and in your mind.
Whether we see/feel the resistance as some self-asserting old "self" or as projected "out there" as others and external resistance, you don't have to go outside your own heart and mind to deal skillfully with this noxious stuff—indeed, it's literally impossible to go outside your own mind and heart. I mean, where would that be?
The kleshas—the hindrances or mental poisons of the mind—always lie and misrepresent. It's NOT the case that you didn't have a breakthrough; it's just that often even very big breakthroughs don't get rid of all the junk in our mental basements. That takes ongoing work and patience, helped and inspired by the light of our big breakthrough.
[See "Non-resistance and the Art of Resisting without Resisting!"] Standing your ground in the face of reaction to progress is a skill that doesn't require belief in metaphysical powers or evil, anymore than "Mara" in Buddhism is a real entity or a metaphysical evil.
Don't be tricked or fooled! Know yourself! Know your "enemy" but know it as not-self! Everything you need to win full liberation and freedom is within each us and within the scope of our practice. With each victory, we learn to trust this ourselves and our practice more fully and deeply.
A breakthrough is a breakthrough. Sure, there may be more work to do. So what? That just means we are human! Love yourself and roll up your sleeves and move on to new fields of awakening. You can't be defeated, and even apparent setbacks will make you stronger as you learn from them.