If you're 21 years old, this should be a great time in your Life Cycle. You're at the 3rd leg of Saturn's 7-year phase (you passed the Square at 7, and then the Opposition at 14), and now you're in the Trine. So what's here to greet you? Pluto conjunct Uranus.
Now, don't mistake this for the transiting phase of Uranus squaring Pluto on a global (mundane) level. What I'm talking about here is a natal union to your position of Uranus from "Wasn't such a good idea to demote me, eh?" Pluto. (The mundane global impact affects everyone; the natal conjunction is another matter--and it's personal IF you're 21, etc.) So what does it mean and how does it work?
Uranus indicates the Roller-coaster of Life Events & Activity. Where it sits in your chart, expect surprises, explosions of some sort, upside-down, and out-of-nowhere. Think of the Tower in the tarot deck. Your legs are knocked out from under you: it can be an emotional, mental, physical, financial, educational, inter-personal, professional juggling session that totally surprises you. In some manner or form, it's where you release your Inner Rebellious Nature--which is part of your own unique creative power.
Pluto is pure volcanic process: molten melting power to totally change anything it touches (including Life Experiences above); huge shifts of personal response. Expect cross-country moves; deaths, inheritances, closing off personal doors and roles, but always, the end of one phase and the beginning of another. Think of a lump of carbon being compressed by pressure over time and weight until its atoms are packed so tight they become...crystalline. A diamond. Your character and soul fabric are being built anew--and you have been transformed in some way. You walked through the Threshold.
Says Robert Hand, "This transit affects us in our formative years when we are most vulnerable to long-term Life Challenges that affect us years later. The combination of these two planets signifies that you want to break away from limiting-restraining circumstances. You may feel that if things aren’t going the way you want, you may impatiently make changes in order to get your way. Don’t count on discipline either. (This is like an anti-Saturn moment.) And a self-righteous nature may be more open in public matters.
However, it would be a shame to waste this energy in challenging everyone around you or blindly rebelling against all restriction. You can learn a great deal about matters that are really important through this transit’s influence. Both planets are profound and powerfully explosive: spend time learning how to know and understand as much as you can about their potentials. You should not ask yet how you can bring about change because you won’t understand it until this transit is well completed.
The outcome may very well be that you become wise beyond your years in your depth of understanding, and through this wisdom you will be in a better position to make either conservative or quite revolutionary changes later on. Even if you do not feel inclined to rebel or push for changes in your immediate environment, you may find that very tremendous changes are taking place within you. This may be quite upsetting, but try to remain calm and see what is really happening. Here again you have an opportunity to gain an understanding that is considerably beyond your years."