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Initially you want to hold for a very long time but as a result of the bear market you loose your capital and half your investment yet the market is showing no sign for you to recover.
What's your next step as a first timer in Bitcoin /Altcoin trading?
It's good that you stated here the term "trading" because it would be a different case if you're just buying and holding.
If you're a trader, you must learn how to use the stop-loss feature.
It would be a different case if you're buying and holding because you still have an option to sell your Bitcoins at a loss, or you will hold it for a long time and as you hold, you will continue to accumulate even more Bitcoins because the perfect time to buy not only Bitcoins, but altcoins as well is during the bear market. Bear markets are very harsh especially if you're one of the many investors that will be buying Bitcoin at a higher price, and if you're a newbie, you might panic because you will see your portfolio being down more than 50%. You will see your capital being reduced to maybe around 70%-80% of your initial capital, but if you're into crypto for quite some time, you will not that market moves in cycles, and in ~3-4 years, the market will rise up again.
If you're a trader, use the stop-loss feature. If you're a long-term holder of Bitcoin, you have an option to make a stop-loss, or will continue holding it, and continue buying it as well.