"There is no problem about mixing present with future tenses. But in order to shift from the present to the past you need to use a time adverb. If you are talking in present and can/want to specify when it happened then use past simple and the correspondent time adverb. Otherwise use present perfect"
That said my teacher when she was correcting an assignment she gave me, in particular this part I wrote:
"Mark isn't happy. He regrets the decision he made. ..."
Present perfect might be better for the second sentence but I've never heard in any lesson nor I've seen in any book there's a general rule like that. I can't find any good counterexample either, so I'd like to know how much truth there is in what she said. Any idea?