As you get older you reflect 
Possibly my worst decision was trying to knock down the price of a 246GTS by £50 to £3,500 in 1979 - seller refused, so I walked - notice one sold at auction last week for £350k 
Hmm… probably my first car… a 1974 VW Beetle…
I was a huge Beetle fan, and I absolutely loved the car and in many ways it was a good move…taught me how to heel and toe (because otherwise it’d stall at every junction until it was warm… it also taught me to keep my distance and read other drivers because the drum brakes were shockingly bad.
It was a bit of a rotten rusty thing though…someone had ‘done it up’ with a nice Porsche Guards red paintjob but underneath it was a bit of a mess… failed several MOTs and I didn’t have enough money to fix it properly… I was gutted.
Once upon a time I bought a Metro…
Selling my brilliant swift gti and buying a Renault 19 16v chamade, hateful piece of French crap!
You’d probably still be quicker than me in that air-cooled piece o’ crap you git 
You missed an opportunity to relive your Beetle experiences at todays H&H Duxford auction.
http://www.handh.co.uk/buy/1978-volkswagen-beetle-1200-l-last-edition/13796
£10,100
http://www.handh.co.uk/buy/1975-volkswagen-beetle-1303/13797
£8,200
http://www.handh.co.uk/buy/1972-volkswagen-beetle-1300/13798
£15,500
all plus 15% fees.
My worst decisions all revolve around NOT buying something when the opportunity arose. Hindsight is a wonderful thing !
Mine was probably an Astra 1.2L. I hated it and drove it like I stole it, but it just soaked it up. It got nicked eventually and I was not particularly upset about it.
Most interesting cars I’ve owned since I’d be happy to still have in the garage.
I nearly bought a black manual F355 once and a 911 (993) Turbo, both would have done well in value terms. But its not about money, its about enjoying driving.
I was offered an Alpina B6 for a steal of a price, I decided I wasn’t old enough at 19 to own a BMW and carried on with my fast fords, I consider that as a missed chance.
My biggest regret is selling all of my old fast fords, had just about every type through my teens and early 20s, would be worth a fortune now 
I was offered an E28 M5 for a bargain back in 1999. Trouble is i was only about 20 years old and at University so I couldn’t afford it. My step dad couldn’t understand why it was such a special car so didn’t buy it either.
It was Don Palmer’s beloved “Boris” which I think ended up back in Germany.
It’s reminiscing on this that has prompted me to get my thumb out and clean up my E39 M5 and get it tip top. I had thought about selling it but I’d quite like to enjoy it for another couple of years until Exige sport 380’s end up on the second hand market methinks 
rough looking E30 M3 in early 00s, for £2300!
A brand new S2 Elise, sold it 3mths later with 500mls on the clock, totally hated the car and very nearly contacted the showroom to do a deal to get my Escort Cosworth back until I saw the S1 Exige 
The actual worst car I bought was a Ford Anglia 105E - 20 miles after buying the gearbox became rather noisy as the acoustic insulation of the packed sawdust and nylon stockings wore out - the chickenwire reinforced isopon composite bodyshell was cutting edge for the time
On a whim I once bought the shittest Cobra replica on the planet and gave about £4k for it, I then spent anoter £3k on it. I drove it about three times, hated it and then couldn’t sell it. haha. Eventually got about £1,800 for it I think.
I owned a mint E30 M3 i bought for £4,500, ragged the arse off it for two years and was super happy to sell it for £4,500. Wish I still had that now.
My main mistakes have also not been buying stuff. A 68 (If I remember correctly) 911S for £5,000 that I umm’d and arr’d on was probably the one I should have bought the most, as you know it would be a wide bodies RSR replica by now. There was one of those for sale at the Classic car show last week for £85k
I wanted to buy a McLaren F1 LM when I was 16. Five years later I told my Dad I’d have an Exige after watching one on Top Gear. Six years after that I bough my first car and I still have it today, it’s yellow. Still think I should have sold my Mother to purchase the F1 though.