You'd be surprised.

I also feared needles. Hell for at least the first few months if not the first year I looked the other way.

Needless to say that didn't last.

In my case at times I was somewhat dedicated to trying to learn to do it. At least the first time I discovered IV cocaine at least. Turned myself into a fucking pincushion. 8)
By then my fear of needles had clearly faded. It's not like I was a little afraid of them BTW. I'm on the autism spectrum & when I was young I had punched a Dr. in the face in response to a needle. I have much better self control than when I was a child but I digress. It quite surprised me that not only did I get over that fear I can now at least hit myself. I was previously terrified! I would take a benzo before getting my blood drawn as an example. I did not like needles! That changed after a while of friends hitting me. Slowly but surely I could look & so on.
In relation to the shaking that you mention I share also share that particular affliction. As a result despite years of daily IV usage I never did master the art of of the entire injection process myself. I got to the point where I learned to hit myself & now prefer to do so when I do IV. I still shake so bad I would fail 9/10 times trying to do the whole injection process myself though. I just hit then I have my wife register & inject. I just hold the needle steady at that point.
So even if you don't believe that you'd ever overcome the fear of needles or master you're shaking; it is a possibility. I have successfully hit & injected at times but the ratio is so low it's not worth the risk to get such a low number in successfully without missing any of the shot in proportion to the number of shots where I'd miss some if not all of the shot. Especially considering my most recent shots have generally been of morphine. Considering the solubility it ends up becoming a full 1ML shot as opposed to the smaller quantities involved with some other substances. It's one thing to get 10 or 20 units in without slipping out when you shake but a completely different matter to get a full syringe in. Regardless; I just wanted to express to you that though you feel that you would never overcome the fear or the shaking; it is indeed a possibility. I figured I'd throw my experience out there for reference. Harm reduction & all that.
Though unlike what other posters have mentioned I didn't find the needle to be something I had an issue switching on or off of. I never got attached to it by any means. I had no problem putting the needle down or using other routes. For me IV administration is generally based on the benefits of IV over other routes of administration in terms of bio-availability, rush, etc. A simple example would be I would IV hydromorphone or morphine due to the B/A & rush of the substances I just mentioned. However oxycodone for example I would generally not go through the trouble of IV'ing though I have consumed it via that route plenty of times (I wasn't turning down free opiods

). I never found oxycodone to have a rush & the bio-availability increase is very small compared to the the opioids I mentioned previously. I'm beginning to ramble & digress. Though if there's thread for it; this would probably be it.
Anyway I just figured I'd throw that out anecdotal experience out there. HR & such as other have mentioned. Again as others have mentioned smoking can cause a similar rush with some substances. I haven't really consumed opioids via the smoking ROA so I couldn't vouch for that. However; as an example if I was asked to compare smoked crack cocaine to IV I would say they both have a rush. The rush is different in some ways but not always what one would expect. In fact it's my experience that the effect of smoked as opposed to IV cocaine actually hits faster. I find IV cocaine takes a longer time to onset, "bell-ringer", etc. than smoking it. So I can verify
madness00's statement in that regard. Oh & again for HR I must throw out there that just because I'm capable of picking up the needle & putting it down no different than any other route does not mean that others experience with IV administration would be at all similar. To the best of my knowledge my experience with IV administration & the needle in general are an exception to what is considered the norm in that regard.
Oh & one last thing I'll mention as well. As
Xorkoth mentioned "All you'll have is a fleeting moment of something really pleasurable, followed by a lifetime of wanting it again in the very best case scenario, or more likely, an addiction to IVing drugs. " Again I won't speak for others in terms of addictive behaviors but I will say that I agree whole heartedlly with the "lifetime of wanting it again". Though I have control over my usage of substances there is always the knowledge of the "feeling". It really does in my experience at least take some of the joy out of life knowing that one can attain a certain feeling with the use of a substance. The difficult part of that being that regardless of the time between uses &/or ever increasing doses one never attains quite that same feeling again. One can in some cases attain a very good feeling for an extended period of time but at that point it often becomes the dominate focus of one's life. The desire to repeat the experience &/or prolong it can become consuming. Whether or not the pleasure of the experiences outweigh the down sides of the changes to one's life that entails is a personal & individual matter. Changing one's life to set one's sole focus to the attainment of pleasure through the use of a substance can be quite the drastic alteration of one's life. Something that is very individualistic as to whether or not that is something that one would be happy with or not.
I'm digressing into philosphy here though. From my knowledge of you from what I've seen on this forum
schizopath the last bit of what I posted is not really applicable to you. To the best of my knowledge your familiar enough with drugs to know what you are or aren't getting into. At least in terms of your not someone who is new to drugs or using them as far as I know. Anyway I'm rambling again. I do love being verbose.
Anyway I just thought I'd throw this post out there. It doesn't hurt to have more information even if it is anecdotal. From my experience at least.