The mind's job is to keep us alive and safe. It's a tool that evolved for survival first. Hence the mind's tendency to focus on mistakes from our past (so that we can avoid them in the future) and to imagine a future that we wish to avoid (to prepare us if it happens). It is like a parent telling his child: "watch out, don't trip on that rock."
There is a lot of love in that, a lot of caring. The mind is innocent. It is just doing it's job.
However, as every child eventually learns, not everything your parents say is true (true: in accordance with fact or reality). When we take what the mind says and believe it is true, then we suffer.
If I believe I shouldn't trip on that rock, then I'm going to be afraid of tripping on it. That is a form of suffering.
Suffering, in all it's forms, is born out of confusion and misunderstanding. The most basic misunderstanding is the one that gives rise to all beliefs: That what the mind says is true.