It is incredibly hard to make money going short. Even if you are right about the direction, most short positions require interest payments to hold, or have some sort of decay built into the structure. So timing is everything and even then, if the underlying security slowly grinds down (instead of a quick abrupt move) you could still lose if the interest/decay on the short position outruns the downward movement on the underlying.
I have been actively trading in the market for a little over a year now, and while winning on a short position is probably the most satisfying trade for me, the overwhelming majority of those trades are losses and at this point I mostly treat them as hedges. I suspect that is true for most market participants as well.
There's actually (at least) three things going against you going short:
- position has significant negative carry (what you're talking about there)
- stock/bond prices are nominal and the government constantly prints the denominator so prices tend to go up even if there's no actual growth
- for equities there is a genuine long term positive drift over time even if the denominator doesn't change
So yes, it's hard to make money going short and timing is everything