A Case For Virgin Potting Soil

Oops, I've done it again.
Years ago I acquired some quince fruits from a neighbor, and I was determined to save some seeds and grow my own quince tree from these fruits.  (If you've never had quince, it's very pleasant, with a mild flavor somewhat like a watered down combination of apple and pear.)  I dried, froze, thawed, and planted my seeds.  I delighted in the emergence of a lone bit of green.  I babied that plant, tracked it's measurements, rejoiced at each new leaf.  By the time it was a year old it was nearly forty inches tall and began to blossom.  I was overjoyed.  My husband at the time dug a special spot in the yard where I could transplant it, sheltered from howling winter winds but with more than enough sunlight to help it grow.  The little tree thrived, and then it began to fruit.  Within a few weeks it was painfully obvious that the precious little quince tree I had raised from seed was, in fact, probably the tallest, most coddled green pepper plant ever grown.  What an embarrassment.  Well, lesson learned - don't reuse potting soil! 
And yet, I never learn.  Those butterfly weed seeds I carefully harvested, dried, and packaged for myself that I planted last month?  Well, the three little green bits that have been living a life of luxury under my grow light look an awful lot like catnip.  *sigh*  Used potting soil fail, once again. 
I've also lost a good many plants, which is par for the course in my life during February.  My 4 year old parsley plant finally gave up the ghost (read: somebody over-watered it), and my lavender that had so much new growth suddenly took a turn for the worse.  Also on my casualty list is the potted palm gifted to me by a friend, and my rosemary plant.  My King Tut papyrus and water lettuce plants in tubs have petered out, but on the upside I have a wicked healthy algae bloom going on.  [insert eye roll here]
Some day I'll get this plant thing down pat.  Until then, I forge ahead, undaunted.