I’d recommend taking it a bit easier. If you hand or wrist is starting to hurt while practicing, your body is telling you something is wrong and you need to stop or change what you are doing. Maybe you are too tense when playing, maybe it’s the placement of your hand/bending of the wrist. Are you going full force without warming up properly?
Something that has helped me a lot in strengthening my wrist/fingers, have been Hanon exercises and playing scales. Both slowly. Yes, I hate playing slow, but it has really done wonders for me.
I can now play several hours straight without feeling any pain or fatigue, where before I could feel it in my wrist. Listen to your body. The whole “no pain no gain” is an antiquated expression, usually coming from roid heads that had the benefits of the roids to help them recuperate. Any educated instructor or physical therapist will tell you that pain is a clear sign something is wrong. Playing any instrument is the same.