Bitcoin investment is not guarentee to be profitable in the long run because no investment is 100% guaranteed. However, we are investing in bitcoin because we have the believe that it's an asset that will increase in price overtime due to the history of bitcoin and our experience of it as we are investing overtime, and that gives us more confidence to continue building and accumulating bitcoin because our strong believe in it as time passes on.
Investment is a combination of profit and loss. You will not find any investment asset or investment medium where there is no possibility of loss. Similarly, Bitcoin investment will not give you a 100% guarantee of profit. If someone guarantees you profit from Bitcoin investment, then you can freely call him a hypocrite. Guaranteeing profit in Bitcoin investment means that you are telling the future of Bitcoin, which is absolutely impossible for a human being. However, we consider Bitcoin as a reliable investment asset where we see the possibility of profit as high, provided that you must be long-term.
The reason why we ask you to invest money that you can lose is considering the potential loss of Bitcoin. Although the possibility of loss is somewhat less in long-term investment, we must be prepared for it. The main goal of investment is to make profit, but you must be aware of the loss and have a plan to take necessary steps.