Words that are used to talk about mental states are usually used in the present simple. These are words like find, realise, regret, think, understand, hope etc.). They talk about how we feel or what our attitude is towards something.
- I find this interesting.
- She understands English.
However, we can use the present continuous to show that we have had a recent change in our thinking, that we are starting to think a new way about something or that we are unsure about something.
- I regret being so careless. and
- I am regretting my decision to change jobs.
In sentence (1), I was careless and made a mistake. It has happened and I feel very terrible about it. I will probably feel bad whenever I think about it.
In sentence (2), I made a decision and at the time, I thought it was a good idea. However, as time passes, I am starting to feel more and more like it was a bad decision. I think I should not have done that.