tax loss selling is real, but can be a very good strategie for you if your AVXL holdings are in a taxable trading account....done this several times these past 2 years with SAVA:
IF, if you believe AVXL is near a bottom,
You buy x shares in the market this week, then sell x shares after 31 days, but you sell the high priced inventory for the tax loss for this tax year. The new shares have a low cost basis, but if AVXL goes to the moon, you sell after one year as LT gain.
If lucky, the new shares will be higher than the buy price and you make capital gain as well, but you have until Dec 30 to close the transaction.