+ all your time of investment would become in vain: long term holder of altcoin should not without a thoughtful look sell off there coin
+ things might not go as you planned: the ball can go two ways, one it can go in your favour and two go against you.
I understand that investing in something more promising -bitcoin for example- is productive, but rather than, selling off just invest in it with available raw capital.
Sometimes it is okay to sell your coin which you have to holding too long just to invest on bitcoin because most of the crypto investors invest on altcoins since they cannot afford to buy bitcoin because it is so expensive so if there is a time when their altcoin is too high and bitcoin looks starts rising can be a good reason for them to sell it.