1/ If you have too much work, it is not your fault, there will always be too much work, that's the way it goes. Learn to pace yourself and do the possible. Don't try to do the impossible, nobody will thank you for it, you will not get a pay rise either. Try and be clever: learn to do the essentials that matter, learn to be efficient, learn to eliminate the chaff, learn to do the job in the time that you are being paid for, learn to leave early on bad days and do more on good days.
2/ If you have too little work, it is not your fault.
Four strategies (mix and match as you please):
2.a/ask the boss what else you could do while waiting for the main task.
2.b/ ask a colleague if they could do with some help.
2.c/ find of your own free will stuff to do or learn that will benefit both you and the company.
2.d/ find another job.
3/ I don't know how much of a social guy or geek you are.
If you are on the geeker end of the scale, find ways to learn and practice social skills:
3.a/ be kind to your colleagues (always smile at them, say hello, be friendly, even if you basically don't rate them - try not to judge, there may come a day when they'll be useful or kind to you in unexpected ways).
3.b/ be helpful to your colleagues (always offer help when they need it, don't offer unwanted help, leave them alone when they need their own time, answer their requests whenever you can or find a bit of time to do so, do find time to do so).
3.c/ Listen more than you speak, but don't let that stop you voicing your opinion when you think it is appropriate (judge it well). Sometimes you might say stupid things, who does not, just learn from those. Sometimes you might shut up rather than say something important, this is a missed opportunity, try and avoid missing such opportunities.