I concur with the suggestions above. You may want to search the net for programs like "Training for a century in x weeks" to see what percentages of different types of exertion may be best.

You need to be sure to fit in rest days, and to spend appropriate amounts of time in various types of training. I have never followed any of these plans, but I will be looking for one, because I want to do a century this year, and it will take some focused work to get there.

Even if you don't follow a plan, you will get the scope of what you should do (something like ride for x minutes at comfortable pace except for three intervals of heavy exertion for y minutes with z minutes of rest in between). If I don't do something specific, I tend to either over-do it, or not do enough.

Now to go search out a training plan for myself.