Betting on things is legal in the UK, and we have something called an accumulator. Basically you pick a number of horses/dogs/etc and then choose X number of races.
If what you pick wins the first race then it's automatically put on the second and so on. If one of your picks loses then you lose the lot.

Anyways in the early 90s a mate of mine won a 15 horse accumulator. He put £1 in and won something like £270000. Astonishingly, astonishingly lucky. Especially as he knew nothing about horses and basically picked them all because of their names!!

He talked about expensive holidays or to go to las Vegas to "carry on his winning streak" and buying expensive cars etc. At that time our friend group consisted of about 8 lads and we all sat him down in a pub and all basically said "stop talking like a twat".
It took a bit of time, negotiation, and compromise but in the end he decided to buy a modest house outright, take about £10k for stupid shit, and invest the rest. Which he did.

Within a few years he was basically set for life. House paid for and money from good investments. He gave up his stressful job and got a job working as a school caretaker.
Life took us all in different directions and countries but he is still set up and enjoying life. Never went to las Vegas though, which is probably definitely a good thing!!