Yes, it is a trick question.
How do you define Best? Here is the online definition. The adjective and noun versions sound like they were written by Bill & Ted in a most excellent way. 🙂

On one hand; You Are Always Doing Your Best
You are doing your best with the energy you can muster at the moment.
You are doing your best with the motivation you currently have.
You are doing your best when you don’t feel well.
You are doing your best based on the knowledge you have gained and the wisdom of your experiences to this point in your journey.
You are doing your best with the discipline you have developed and the purpose you have chosen.
On the other hand; You Can Always Do Better
You could most likely muster the energy to do one more rep, to add one more mile, to finish that nagging last task before quitting for the day.
You could push yourself to find the motivation to pursue that dream, complete that goal, and knock down that next domino.
You probably can do more than your body and mind are currently saying you can.
You could increase your knowledge and improve your skillset. You could reflect on your experiences to gain one more small insight.
You could increase your discipline and truly identify the purpose you want to embody.
Yes, It Is A Trick Question
You are doing your best, and you could do better.
The key to this question that you most likely ask yourself every day in some shape or form is:
Accept that the past was your best and your future can be better.
Doing your best is accepting every moment as having been lived to its fullest potential while working to increase the potential of the current and future moments. Every past moment is a building block for the next. Take that supposed failure and learn from it.
Doing your best is not about meeting expectations or achieving goals. Success and failure are labels and choices that your mind assigns.
Doing your best is about putting your focus and energy into whatever life throws you. The amount of energy and focus you have will change day to day and from moment to moment. It is the best you have, and it could be better.
Challenge yourself, leave the past, love the present, and look forward to the future by embracing the current challenge as an opportunity to do your “better” best.
Enjoy the journey, not the destination.
So I ask again, ARE YOU DOING YOUR BEST?