Iʼm getting better, but it will never be perfect. What i noticed, though, is that iʼm usually spot on when estimating othersʼ time.
Us humans tend to show ourselves as better than we actually are. Thatʼs a fact and doesnʼt really change between different cultures, either. So at our company we are currently trying to estimate how much a task will take for someone else (who will actually work on that task).
Another thing you should take into consideration is that time estimates are usually net times: “if i can work on this uninterrupted, it will take this much”. However, this is almost never the case. We tend to get interrupted, and context switching is not cheap for most people. Thus, you should multiply the estimates at least by two.