The practice partner who challenges you fairly is contributing to your next improvement.

Someone who lets you win is being pleasant and teaching you nothing. Improvement needs a level of difficulty just above what you can currently handle, which requires a partner willing to make you uncomfortable without making you miserable. That balance is rarer than raw ability and worth more. Fair pressure applied regularly is most of what separates people who improve from people who simply keep playing.

Ask your regular partner to stop going easy on you, and say you would rather lose usefully. Thank them when it stings. Then do the same in return, which is harder than it sounds.