Hello. This can be a common problem, with a few reasons.
Are you around other people often, people who are negative, toxic, and drain your energy? Either living with or working with people like that.
Also, do you allow your energy to be drained by doing useless things, such as too much time spent on social media and so on? This seems to drain people, not just mental energy but also our energy goes where our mind goes, so it does have an effect.
Try spending more time to yourself for one day as an experiment, do your yoga and meditations, stay offline if possible, and affirm to yourself that your energy stays with you to empower and advance you. See if that makes a difference. At the very least, spend time to yourself after meditation, without immediately going online or being around people. This can be difficult for most people with normal lives, but even 5 minutes will help.
It's important to pay attention to ourselves and how we might do better with our time and energy. HP HoodedCobra posted an important and easy meditation relating to this, I'll link it as it might help you pinpoint where your energy is going: https://ancient-forums.com/viewtopic.php?f=24&t=63176
And if you are around draining people through in your day, close your chakras before being around them, and also affirm to yourself while meditating that other people do not drain your energy. This might be of help as well: https://satanisgod.org/www.angelfire.com/empire/serpentis666/Detaching.html
I'm sure other people here will also have advice for you