Why time runs fast and slow in different situations?

Time is always running. Its speed neither changes nor can it be changed, or can it?

 When we are engrossed in some work time flies but at the same time, for somebody else time must be moving extremely slow because they are going through a boring work day. The simplest explanation for this is diversion. When we are diverted, we don't pay attention to time. Thats why it moves so fast. If we are not diverted, time moves very slowly. The same can be experienced while watching a film. A good film will cause time to just fly by but a bad film will bore you.

That was the reasonable explanation but what if we go the fictional route. Einstein said time is relative and that it changes in different points in the universe. Maybe doing important work will full dedication has the same consequence of time running quickly. If this were true, all of us should be at different points in the day but that does not happen. Thats why I started the paragraph stating that I was taking the fictional route. 

Time is a relative quantity and cannot be controlled. But it looks like we can control the speed at which time runs for us. If you're busy then you know time is going to fly. I have had experiences of time flying while studying during examinations. Time is damn slow during lectures. I believe most people have the same experience. 

If time runs differently for different people then there must be a way to control it. We don't have the power to control time yet but the speed of time can be controlled by us. We do it without even knowing, knowing that time will fly in certain situations. Its pretty confusing but I hope I was able to convey what I wanted to say.