Short term investing is like trading, but there is risk involved in investing for a short period of time. However, having funds is the most important thing when it comes to investing. If you don't have funds, you can't invest. If you have enough funds, you can invest some amount from there. When you invest you may face loss due to volatility in the market but if you have funds at that time then you can reinvest and get profit from it.
Are you a trader? Because you sounded just like one because I don't no the reason why volatility will make you lose your Bitcoin investment and how reinvesting again will bring you back the profit from it, don't you think your statement is a bit unclear?, however I will like to clarify you about volatility concerning your investment, so actually don't feel that is only those who has invested a huge capitals are able to withstand volatility on Bitcoin investment because it doesn't work that way, as long as you are a holder you are immune to volatility, so no matter how small you are accumulating Bitcoin volatility will not destroy your investment because even if the price drops it will still bounce back and your investment remains intact so don't feel that there is any negative impact volatility can make into your Bitcoin investment.