Pot isn’t feeling like it used to for me, what do I do?

For the last couple years in the times I smoked it always affected me and changed how I thought in a pleasant way. I started smoking again recently and at first it was the same but now after like 3 weeks or so I feel like it doesn’t affect my state of mind in the same way it did. I think the same except like a body high. Why has this happened and what can I do to get back to how I was?