A question that gets asked a lot, and one that you should be asking and thinking about, is how to scale your workouts appropriately.
1. Your Coach/Trainer should definitely be able to guide you through this. Talk to them. They should already know a bit about you and your abilities and can offer guidelines.
2. Keep a WOD log so as you go you know what you have done in the past, how it felt and what you should be striving for next time. Be diligent about writing stuff down after every workout. And not just your weights and reps, be sure to include notes on weather, your general health, any aches or residual soreness, time of day, if you had eaten before hand, and things of that nature.
3. Know what your goals are and have an idea of what you need to do to achieve them. Hopefully when you joined the gym you were asked about those goals and your Coaches/Trainers are best able to help you achieve them.
4. If you know your one rep max for certain lifts, that can certainly be a great guideline. If your 1RM thruster is 105#, a WOD like Fran with 21-15-9 reps of 95# thrusters is going to be much too difficult to complete at this time with your current abilities. And just because you can’t do that WOD as prescribed in no way means you are not getting an excellent and the desired workout for that day. Your coach should also be able to give you rough percentages based on your 1RM according to the plan for the WOD. if it’s a heavy day they might suggest 75-85% of your 1RM. If the WOD that day is supposed to be light and quick, they may suggest 50-60% in order to complete the WOD in the amount of time intended and with the appropriate amount of intensity.
4. A good gym should always know what the overall goal of the gym is, what the monthly plans are and what each daily WOD is designed to accomplish. A great gym and a great Coach/Trainer will be able to tell you what each days’ activities are designed to do, how you should feel while doing them, and how long the workout should take you in order to achieve the desired effect. In a WOD like Fran again, the goal is an all out sprint, and the best athletes in the world can get it done in around 3 minutes. If that WOD is taking you 15 minutes, you are most definitely not getting the desired effect of that planned workout.
If the WOD programmer is doing their job well, they will have a very specific goal for each workout, whether that be strength, a quick burner, being in the aerobic zone, pushing yourself to the anaerobic zone, or working on recovery rates. These are all things to be worked on and they all have a place in your workout routine, you need to be sure you are getting the desired effect of each workout to make the greatest gains overall.
Ultimately, you control your workout, you know how you are feeling each day and you are in charge. Listen to your body.