While practising pranayama's - the control and regulation or breath

I've had people tell me, doing 10,000 rounds of certain pranayama's is good for so and so health concern. This very scary 'advice'. The breath has a direct impact on the mind and therefore this medium is best used with care, under an able teacher. Shri Yogendraji thus recommended a maximum of 10 rounds of one pranayama in a sitting, and thirty rounds cumulatively in a sitting. 

Here's what the Hath Yog Pradipika by Swami Swatmarama says on Pranayama's: 

मथा श्चसॊहो गजो व्याघ्रो बवद्वे श्म् शन्ै शन्ै
तथवै सश्चेवतो वामयु न्यथा हश्चन्त साधकभ ् १५

Yathā simho ghajo vyāghro bhavedvaśyah śanaih śanaih
Tathaiva sevito vāyuranyathā hanti sādhakam (Verse 15)

Just as lions, elephants, and tigers are tamed [little by little, with patience and energy], so too, prana (bio-energy or life force) should be practised under the guidance of an able teacher and done with great care. Otherwise it can kill the practitioner.