I realize this is a broad question, but my life has changed drastically in the last few months, and I'm looking to experience more before I get too old. I know the usual answers like getting married, having kids, and so on.
I'm more interested in skills, hobbies, fields of education, practices, habits, and experiences that have shaped (for the better) the person you are today.
Python. Start with python. It's a big language right now and I don't see that changing. It's a good introduction into programming with easily transferrable syntax, unlike something like Visual Basic. It's backed by a lot of big name companies, not the least of which is Google. It's so ubiquitous that you can find endless resources with which you can learn it.
Alternatively, C is a very important language. C will never die. It's a harder and less forgiving language to learn, but it can't be beat performance-wise. C++ would be next in line.
C# is a useful language in the Windows world since it relies on the .NET Framework to function. That said, .NET Core has been moved to Linux now. Even still, many languages use a lot of the same syntax characteristics, like Java and Vala. These languages just aren't universal, though.