Bitcoin investment is inherently risky and we should invest with that risk in mind. But we must be very careful in investing in Bitcoin, if we can invest carefully, Bitcoin can achieve a lot of success. Those who are new to Bitcoin investment must acquire enough knowledge about Bitcoin before investing in Bitcoin. If they do not acquire enough knowledge about Bitcoin then they will not achieve good success in Bitcoin investment. Sometimes it is seen that even experienced investors lose patience so definitely our patience is very important when investing in Bitcoin. If we can invest with patience and long-term planning, surely we will be successful in investing.
What do you mean when you say we should invest in Bitcoin with careful, there is nothing to be careful about investing in Bitcoin because is not like putting your money into investment that would claim all your funds because is one of the most safest digital investment you can ever think of, so instead of the word being careful I think you have use the word investing with what you can afford because that's the only way to represent the careful you are talking about, also not everybody that believes that Bitcoin is as risky as you believe because to some persons is the best investment that has lesser risk compare to others, so perhaps it seems is from the experience you had from the kind of investment you were doing that made you think that way
Perhaps you might think that there are no risk in bitcoin because of how well it has performed over the years but you can't underestimate the fact that carefulness is very important as much as the investment itself. Of course @synchronym might not express what he meant by being careful but we can still relate bitcoin risk to other areas apart from the obvious part that it's a paradigm and not a Ponzi scheme as lots of people saw it from the past. Risk that are involved in bitcoin could be few and not as much as shitcoins can be risky hence I can would relate you to the irreversible nature of bitcoin, wallet compromise etcetera.
Apparently you might not want to consider this as risk that one should be careful with for some reason of being acquainted if the basic bitcoin knowledge but for someone who is probably a newbie or a novice investor it's paramount to be careful and examine every step which one would probably take in the cost of bitcoin purchase and/or investment.