I think this is a psychological matter where your emotions and your alternative source of income flows have to determine your goals and as well your time of holding before taking a sells decision.
Investment plans is mainly determine by the nature of the investments solely influenced by the individual, you may be wanting to go on an investment plan for 5 years but the reasons for that would be limited to more than the years assigned for the investment, so for long term investment especially involving Bitcoin be rest assured of your decisions before executing the plans of investing.
This is where purposeful investment comes in. I support and encourage purposeful investment and savings. Some people keeps investing without a goal and that is why it is always like they are caught-up in the circle that they don't know when to exit the market. When you invest with goal, you will exit your investment when your goal is achieved. So, I support the idea that short and term investment differs and depends on plans. What would be a short term investment for Mr A, could be a long term investment for Mr. B. Although, I have stated the time fram above.
Also, the best form of saving is saving with a purpose. When the purpose is accomplished, you make it happen and start saving for another.