Learning to think in all 12 major keys is not that hard compared to learning languages (in fact it is super easy compared to languages!). And since there are 12 months in the year, why not devote one month to learning the key of D, one month learning the key of Eb, and so on throughout the year? At the end of the year you’ll have a pretty good grasp of all 12 keys, and you’ll begin to think in those keys instead of fighting with the sharps and flats as perhaps you used to.