It used to be called "scholar's neck" or "reading neck." Today it's called "texting neck." Whatever you call it, forward head posture (FHP) can wreck your training.
For some reason, standing up straight is hard. Many things can affect where your body naturally rests, anything from a badly designed training program, to stress, to just plain using your phone or computer too much. Shoulder pain, neck pain, and lower back pain can all stem from FHP, and if you have it then you're more likely to get training injuries.
Here are two things you can do to straighten up:
Wall Drill
Stand with your back to a wall.
Make sure your lower back and shoulder blades are touching the wall. Have your feet slightly away from the wall.
Now touch the wall with the back of your head. Start to tuck your chin into your chest without letting your head lose contact with the wall.
Repeat this for 10-15 reps and focus on the stretch in the back of your neck.
Step away from the wall and try to replicate that same feeling without needing to use the wall.
Band Drill
Attach a light resistance band to something in front of you and roll your shoulders back and down, hands at your sides.
Actively try to pull the band back behind you with straight arms. Be aware of your lats here.
Step back slightly and maintain a good shoulder position.
Now replicate the same neck stretch as before, again for 15 reps.
Once you've done that, practice walking around with that posture. You will feel ridiculous, but exaggerating is the best start for making any kind of improvement.
The more you do it the less you'll need it in years to come! About 10-15 reps are great for a quick daily blast, but spending 5-10 minutes on it at a time is fine too.