I did Istikhara for a very difficult decision which I had felt unsure about. The outcome of the Istikhara was positive. However, since then I feel intense anxiety and distress in carrying out this decision. What should I do next?
Your feeling intense anxiety and distress about carrying on the result of the Istekhara, means that you were not reluctant about the matter but you were against it. This means that you did not need an Istekhara right from beginning. Istekhara then is invalid, because you had already decided against the matter.
Wassalam.