There is a very popular theory of time travel, called the "butterfly" theory, which says that any changes made in the timeline will necessary have dramatic consequences in the future -- changes which may seem totally out-of-scale. The example comes from the branch of mathematics called chaos theory. According to chaos theory, something as small as a butterfly flapping its wings in Southeast Asia can cause something as tremendous as a hurricane in the Caribbean, when you're dealing with a complicated "chaotic" system like Earth's atmosphere and the weather.

While it's true that small changes in the time stream can have domino effects, the "butterfly theory" discounts physics of what metaphysical scientists call "temporal inertia" and what mystics call "fate". Either way, the time line resists change, and a certain amount of energy is put into preserving the time line against changes. What is generally seen when small changes are made in the time stream is small changes down the line. But, the force of temporal inertia starts to interfere with these changes so that, as the time stream moves into the future, things equal out.

This opposing theory is often called the "banana peel" theory, I think so named in a derogatory tone of voice. The idea is that if you go back in time and try to make gross changes, you'll find a banana peel under your foot which will cause you to slip and fail in whatever you're trying to do. It's a bad example, but the principle is perhaps correct.