Hackers always use this argument against everything because you can in fact know some things about what one person, yourself, will do in the future.

Thus they argue that you should not trust your things to other people but do it yourself, because, barring major illness, you can reasonably assume that you will try to do what is best for yourself in the future.

>because you can in fact know some things about what one person, yourself, will do in the future.

Nope. At best you merely know what your current self intends to do in the future. Whether you'll do them then, or whether you'll even still want to do them then, or be able to do them then, or have regretted ever wanting to do them, and many other such things, we don't know.