If a currency is bearish, do I sell it?

I can see that GBP is bearish at the moment. What can I do with that knowledge?

Either follow the weakness and sell or wait until the weakness ends and then buy.

But in reality you can’t just buy strong and sell weak on an ad hoc basis. A strategy should take account of relative weaknesses and strengths but it can’t just be that factor alone, and if you’re trading very short-term you might be able to pretty much ignore it.

Yeah you may sell it but the point is that your conclusion relates to the past prices. In case of assumption that future prices are independent from past prices means that trends do not exist. It’s not easy to prove one of these assumptions, probably truth lies somewhere in between.

There’s a little more to it than that. Which timeframes are bearish? On which timeframe were you contemplating shorting it?