Balance is the key.

Simply saving up a polarity is asking for trouble and frustration.

When alone,

balance fire and water.

When coupled,

balance through exchange.

Note on coupled practice:

Reciprocal exchange is the natural progression of dual cultivation.

Bring the recondite to overflowing,

drink from the spring.

She gets warmed and expanded,

He gets nourished and settled.

Both joy.

Note on solo practice:

In solo practice, unaroused jing balances much easier than aroused.

Aroused jing has changed alchemical qualities (from the original cool & gentle, to fiery & adamant).  Your own heart energy is no longer truly a complementary alchemical opposite; the other gender's aroused jing is.  Additionally, through arousal, a deep forceful aspect of the psyche (the libido) is set in motion, that wants the other gender (not sublimation); this aspect deserves respect.  Re-establishing real harmony (alchemically, and in the deep psyche) on one's own, after solo aroused practice - is genuinely problematic.

In solo work, emphasize unaroused practices.