I gotta add to this, as a semi-professional bass guitarist (I get paid to play in a band) I have high expectations as to how well I perform onstage, so I rehearse a few hours every other day. I play the violin about every day, however, for an hour and no more. And if I don't then I definitely know it.

But with the bass, because of the amount of rehearsal and technique-building I have created in my life, the muscle memory is such that some time off really doesn't effect me negatively. I still work on technique, though, as part of my regular rehearsal on bass.

The fact is, what you are doing right now, is building that muscle memory and "feel." Had we done this 15 years ago, we'd be able to pick up the instrument after time off and not really feel much of an effect. 

So don't be hard on yourself. Just concentrate on trying to play as correctly as you possibly can, and have patience, it will come.

It is supposed to be fun. It's learning, and achieving. And that is fun. No one said fun was easy, however.

With the bass, I always tell anyone I am teaching to know their fretboard. Find an A on every string, in other words. Beyond that, knowing simple basic theory can help you find all the right notes in the key signature you're playing in.

That's what I had to go back and re-learn on bass, because once my orchestra classes went from technique and education oriented classes to a simple performance-based class, none of that was taught. And while it always seems daunting to look at a book full of modes, scales and patterns, you eventually start seeing a re-occuring theme in them, and discover it's not as hard as we made it out to be in the first place.

^^^ FTW!