First, one of the best advice I've heard: If you get frustrated, STOP! Doesn't matter if you leave the bass in a corner for a whole week, playing with frustration is no good. I've found that taking rests works great, sometimes I've quit for a while, and then when I get back to it, I find it easier to play songs or lines I used to struggle with.
What has worked for me, both on guitar and bass, is try increasing the difficulty sloooowly, and playing different genres.
Try learning bass lines from any song, doesn't matter if you can't learn the whole song because it's difficult, you should at least give a try to the lines that don't look too hard, with time, it will come.
Another thing, why do you think you suck? More precisely, are you unhappy with your technique or your musicality? (is that even a word?)
If you want technique, then practice, practice, practice, those boring exercises on the internet do work; also try learning harder songs!
If it's your improvisation, coming up with songs or bass lines, just play around the fretboard, listen to LOTS of different music, try following or playing different melodies on the bass (play the guitar, the drums, keys, etc.). You can even get lines from every day noises (like in the movie August Rush).
Death Metal is what got me into playing bass, (DiGiorgio and Webster being the bassists I most look up to), so I'm kind of struggling playing what I want. I know it will take some time, but I'm slowly build up my technique, playing easy songs (sometimes attempting hard lines, even if I sound awful) and working my way up to harder stuff.
When I get frustrated, I stop playing for a while or work on slow stuff or technique exercises.
ps: The gear is not really a factor, I learned that the hard way... Sure, when you get a new pedal, amp or instrument everything is shiny, but the feelings you had before will come back if you only rely on your gear.