It's normal for a trader to experience losses because no one can predict the market and even profitable traders agree that. But there are many traders who win a lot in a bullish market rather bearish. Here in crypto, if the market is bullish you can possibly earn multiple of your capital and can be up to 50x or 100x, it happened in year 2021. A lot of traders even newbie traders are getting rich because most of their strat are working since the market direction was always going up. But when bearish came up they disappear.
Aside from that, I only base on my analysis in the chart, I won't say Bitcoin is seasonal.
In the sense that it has bearish and bullish trends that occur at different times in different years, we can call Bitcoin seasonal. Maybe it doesn't have a fixed season when it goes up or goes down, but since it is volatile and it is always likely to go down when it's up and go up when it's down, we can clearly say that the price of Bitcoin is seasonal.
It obviously is normal to incur losses when you are trading or doing any kind of business, nothing can provide you with constant profits and you will surely have to face some hard times during the course of whatever you are doing.
what happens to Bitcoin is unpredictable. Even if it's called bear season or bull season, we can only make trading predictions and investment plans based on what's happening in the market.
simply those who invest in the market will buy when the market is in bear season. and sell it during the bull season. but that is not a guarantee someone will benefit. because seasonal periods as you said can never be predicted.