Your right here. No investment is 100% guarantee. Bitcoin has done financially well over the years till now, and with the global respect and adoption shouldn't make us treat it like some sort of financial savior. Many situations and problem may come and affect the system which we do not know what may be the outcome in the future. In as much as we expect the greater potential benefit of Bitcoin as we invest and hodl for long term we should also have it at the back of our mind that the system was created by man and anything that is been deployed by man has limitations. Bitcoin is good to invest but its not made into perfection.
This is why it's advisable to use only your discretionary income to invest so that if in future bitcoin price goes against you or did not perform as expected, you wouldn't regret investing in bitcoin. However, the odd of bitcoin price going uptrend in future is higher than going downtrend but that doesn't mean that you should see bitcoin as a risk free investment, because if you miscalculate the money that you are suppose to use to invest in bitcoin and use more than your discretionary income, you will lose your investment.
I feel that the risk in bitcoin is not only about the price going down but also your inability to make proper plans and invest in the right way for long term. This is why we should put all these into considerations so that we can invest and become successful in future without regrets.