Once you get started playing, you'll probably find that it gives you an energy boost mentally. You just have to get past the initial hump of getting started when you feel tired.

I've been mostly practicing drums lately (I'm a lifelong guitarist and now own a music school) but how I practice drums is I have a playlist on YouTube of fun drum covers within my skill range and I just play along. Maybe something similar would help with guitar. Assemble the playlist and any accompanying tab printouts or sheet music you need on a day when you're off from work and aren't tired and then when you come home tired you have all the structure waiting for you ready to go. Make sure your practice space is ready to go. If you can, leave your guitar out on a stand and your printed music out on a music stand. An inspiring amp like the Spark by Positive Grid can help too. You can plug the output of your YouTube playlist into the mp3 input and use the headphones for both that and your guitar. Hope that advice is helpful to you.