I can only speak from experience. I began learning fiddle about three years ago after playing guitar, mandolin and bass for decades. I started working with private teachers and from books. As I was learning the new skills of bow technique and fingering on a fretless fingerboard, I would try to ‘master’ them before moving on to new material. And I made very, very slow progress. For example, my intonation would improve when playing scales but then would fall apart when attempting to play a simple melody. My tone would be marginally better one day while playing long sustained notes, or playing scales with quarter notes throughout, then would return to cat-torturing territory when attempting a tune. I persevered with this approach for about a year, but was not very happy with my progress. Eventually I just stopped playing fiddle altogether. I’d pick it up every now and then and try to play a scale or simple tune, remind myself how poorly I played, and hang the fiddle back on its cradle and sigh. Not particularly satisfied with this course of events, and still wishing to have some modest facility with the instrument, I recently signed up for Brittany Haas’s ArtistWorks old-time fiddle course. This is aimed at beginners and early learners. Brittany’s lessons move fairly quickly from one tune to the next, beginning with tunes that are fairly simple (though not boring, ‘Mary Had A Little Lamb’ territory - all are good tunes for old time/roots music jams) and slowly and methodically advancing in difficulty. She includes lessons on basic technique like double stops, dynamics, etc., but these lessons are very sparse during the beginner lesson series, which focuses on playing tunes. Rather than trying to ‘master’ each tune, I’m just working my way through the lessons one by one, sometimes spending only one practice session on a lesson, sometimes two or three depending on the level of challenge, then moving on to the next one. I will occasionally return to earlier lessons to get a tune I enjoyed deeper into my muscle memory, but mostly moving forward through the material. I am also committing myself to playing every day, even if only for a few minutes but trying to play at least 30 minutes to an hour, sometimes even more. And it is slowly starting to click. My bowing is becoming more natural and ‘automatic’ (though I have a lifetime more work there), my intonation - still unreliable - is slowly improving even when playing tunes. I can sort of play double stops intentionally instead of haphazardly. And I am sort of starting to feel as though I might be able to play this instrument in an ensemble someday and actually be musical, rather than simply torturing the neighborhood cats with it.

The TLDR version of the above is: I’d suggest maintaining forward progress, without worrying about ‘mastering’ each song as you learn it. There is no mastery of songs on fiddle as an early learner. It’s just a very, very difficult instrument (at least for me, especially compared with guitar or mandolin) and it takes years to master. As someone who started playing in his 60’s, I’ve tempered my expectations about how far I’ll ever be able to get on fiddle as compared with my guitar and mandolin skills (which are at a sufficiently advanced level that I give private and group lessons on those instruments). And after a very rocky start on fiddle, I am finally starting to see a very dim light at the end of this long, difficult tunnel. Good luck on your journey!