Should I buy this bike (boat, watch, house)? Consider these questions

Large purchases require extra thinking. Why? Because a $5 mistake is different from a $5000 mistake for most people.

Try it cheap. Lease.
What are you trying to achieve? Some people want freedom, speed, etc. For example, people want to burn off steam and have fun and go fast. Learn how to bike or mountiain bike or even a motorcycle. Cheaper and gets at the thing better than buying a fast sports car. Freedom? Go on a walk.
Is it just a bad value / cost?
What else could you use the money for? Example, default to would you rather have this extra outfit or would I rather do something else?
Flip it around. I do this when deciding whether to return things. It was a jacket and a great deal for $80. Maybe I'll keep it. I could use it. Or if I had it, would I sell it for $80? Yes, absolutely, get rid of it I already have tons of jackets.

If you actually need something, then there is usually only one reason. It makes it faster. For example, my phone was lost. No chance of getting it back and I need to get one today. Just chose the best model you can in the time you have at the store. No use spending weeks.

Something broke and you need one today. Do it.

Is the item maintenance heavy or does it require a whole bunch of new purchases? and storage? avoid it.
People that are into it are not that great / don't want to hang out with them.

Lots of planning or logistics to be abl to use it. Ex. a bike that is stored away vs one that is maintained and ready to go. A vacation house that requires flights and driving to get to vs one that is a few hours away.