I snapped up a couple of old school stock market heroes earlier this year as I thought their shares looked unmissable value following a recent slump.

I’d been watching both FTSE 100 stocks for years and was thrilled to buy them at what I thought was a bargain price. I thought they’d soon get their act together but they haven’t. Now I’m getting annoyed with them. And yes, I know that’s not the most mature response.

The first former FTSE darling is spirits giant Diageo (LSE: DGE). I snapped it up in November last year shortly after it issued a profit warning following a drop in sales across its Latin American and Caribbean markets.

I need a drink after buying Diageo shares

As the region’s economy struggled, drinkers started swapping premium Diageo brands for the local firewater, hitting sales. An inventory mix-up didn’t help.

Never mind, I thought, Diageo is a huge diversified drinks maker and Latin American is only a tenth of its total market. But sales elsewhere haven’t been brilliant either. Particularly in China. Recent reports that Beijing is lining up provisional anti-dumping tariffs on imported brandy is another worry.

I’m also worried about Gen Z’s attitude to alcohol. Instead of necking all they can and falling over like young people did in my day, they’re cutting back for fear of making fools of themselves on social media. It says a lot that Diageo’s biggest success story right now is Guinness 0,0.

The Diageo share price is down 26.58% in a year, which is a huge drop. I’m down 16.81% after snapping it up at a supposedly reduced price.

Trading at 17.54 times earning it looks cheap by prior standards. But maybe we shouldn’t measure Diageo against those anymore.

Should I sell? As a long-term buy-and-hold investor, that would be against my principles. Plus sod’s law says the moment I do sell its shares will rocket.

The GSK share price needs a pick-me-up

I’ll give Diageo time to straighten itself out. Stock markets generally have gone sideways lately, so now isn’t the time to panic and sell good companies. Which brings me to pharmaceutical giant GSK (LSE: GSK).

In its former guise of GlaxoSmithKlein, it was a top dog among FTSE 100 income investors back in the day.

CEO Emma Walmsley has been battling to replenish its drugs pipeline since taking the helm in 2017, but success remains elusive. I hoped its shares would kick on once the US legal case over blockbuster heartburn drug Zantac were resolved. Instead, they’ve continued to slide.

The GSK share price is down a modest 3.14% over 12 months. Personally, I’m down 16.17%. I didn’t expect that from a stock I thought was a pretty defensive play.

New investors may be tempted by a higher yield of 4.22% but that’s down to the falling share price rather than dividend growth.

GSK now looks really cheap trading at just 8.9 times earnings. One day we may all look back and see this as a brilliant opportunity. Let’s hope so. I’d average down on both Diageo and GSK if I could, but today I’m fully invested. So I’ll close my eyes, take a deep breath me and wait. Patience is a virtue, I’m told.