"Unstable" is such a vague word. And just because you have 6 planets in Capricorn does not make you "stable." You have to look at what planets they are. Since you have Saturn Uranus & Neptune in Cap, that means you were born, what, Feb 7th or 8th, 1990? That's only if you have a Cancer Moon... if you have a Pisces Moon you are Jan 30th or 31st.
Well Saturn may be happy in Capricorn, and Mars & Mercury can cope with it, but Neptune & Uranus chafe at being in Capricorn. Neptune is about the ephemeral, the spiritual... kind of useless to Capricorn, and Uranus is about freedom and chaos, also tough for ol' Capricorn control. And Venus in Cap? Tough being loving and calculating at the same time.
You really have to look at the entire chart, and what all the planets are doing, and how they aspect each other. And the Sun, Moon & Rising together are the three most important points in anyone's chart... so... all that Capricorn will have to serve the Sun, Moon and Rising.
And if you have that Cancerian Moon? Is it conjunct Jupiter? That would rev up the emotional side of you!
23 years as an Astrologer and 55 years as a Capricorn