annual loss limit is 3000, you can carry forward to next year

Annual loss limit is 3000 (for a couple, $1500 for single).  That means you can only deduct $3000 of your capital loss from your other income for income tax. 

If your loss on this fund in 2018 is 4000, you can only deduct $3000 in 2018.  

However, under loss carryover rule, you can carryover the remaning $1000 loss to be deducted in 2019.  Since $1000 < $3000 limit, all $1000 can be deducted in 2019 (assuming you don't have other loss in 2019).

Exactly how you can lose $4000 from 2008 to 2018, the longest bull market since WWII, is another matter, I don't want to speculate. 

https://www.thestreet.com/investing/longest-bull-market-14804308