Forex and cryptocurrency are two different market although forex is more profitable considering it's more predictable and less volatile than cryptocurrency market. The skills needed in both market differs too, while as forex depends on a more technical approach, cryptocurrency can still be profitable without relying on technical analysis.

I'll suggest you learn both trading technique, they'll come in handle in different market condition, a successful trader in my opinion is a trader that have master the craft of trading and failure is hardly experience during his/her professional time of trading. A successful tradet has to be willing to learn from their previous mistake to improve on themselves.

To be a successful trader doesn't only depends on profiting from your traders since every trader can be profitable but it depends on how you have developed yourself over the years, master a strategy that you can deploy anything and it works perfectly for you, been able to adjust to any market condition and still profit etc.