It is far easier to tell the truth than it is to lie. When you lie, you have to be able to keep your story straight, and for most people, that's a hard thing to do. Tell the truth and you will relieve the stress that comes with telling a lie.
It's easier to remember the truth because you lived it. A lie is made up, a lot of times on-the-spot. If you lie, you have to remember your lies and how they intertwine with other lies and truth. It can be quite stressful, especially to try to remember all the lies you've told. Most people who tell lies instead of the truth end up contradicting their own stories because of different lies. Just tell the truth and you don't have to worry about your stories not lining up. They will always line up because they happened.