You believe you cannot travel in time because if you go back in time your actions will alter the future, possibly even resulting in you not existing.
Rick blinked. "What?"
Imagine time is a pool and an action is throwing a stone into it. Even the tiniest action, the tiniest stone, causes ripples. The ripples- the consequences of your actions- are huge at first but lessen as the ripples spread, as they move through time. But the whole pool feels your actions' consequences: at the edge, the tiny waves are still seen.
But your time is not a small pool.