There may be few speculations her as to what is causing this and as a result of it different options to help with halting the procrastination.
1) you have mentioned that you have tried antidepressants (one of the symptoms in depression is anhedonia (lack of interest in activities even pleasurable ones), poor concentration/memory problems, fatigue. If what you are experiencing is as a result of depression, then medication can help (but one has to be consistent and willing to work with a doctor to find the right medication at the right dosage)
2) If the tasks you are doing are primarily work related and or boring, you may not find them challenging enough and therefore feel unmotivated. This is not unusual. A change of pace and some variety could help (for instance doing things in different order and trying out new things)
3) Hypnosis is quite effective in assisting someone in becoming motivated and engaged and if you are open to trying this, you may want to find a good hypnotherapist and work with them. It usually takes several sessions to start seeing some difference.
Thank you. It was a helpful guideline. Yet, to give more specific information, I'm a freelance landscape photographer quite renown in my country. Most of the procrastination is work related, due to the character of business. It could be summarized as indefinite & volatile schedule - too much freedom of choices - low income - medium social reward. For others, it must be one of the most exciting jobs to be doing. Yes, I appreciate but with some reservations. Actually, it's problematic & stressful more than being exciting; because of high expectation, lack of roadmap for future, difficulty in proper goal setting, and inability to gauge my ability despite of obvious numerous success markers.
I've always been prone to depression for no apparent reason (possibly existential depression with biochemical background), an obvious high IQ - low social ability type, and was diagnosed & treated for OCD when I was a teenager. I no longer show any of the obvious OC behaviours, but it has likely been transfomed into OCPD unfortunately, rather than having completely wiped out.
Too much freedom of choices gives me problem as well as the opposite case. Same applies for stress level. I've found that some extent of structured lifestyle is better, analogous to walking in a valley to a certain destination rather than being in the middle of an ocean with no sense of direction.
Each time I sit in front of the computer to either process photos, or write an article, I come across with questioning their value in the context of 'meaning of life'. Instead, lingering with trivial subjects gives a temporary relief from anxiety, but then it rebounds worse.
How can I just concentrate on what I'm meant to do? Maybe an external force?
I'd be happy if you may elaborate your answer in the light of this extra information.
If structure is more helpful to you in keeping you more focused, perhaps following some kind of a routine may be helpful. In order not to become bored and bogged down by it, maybe alternating the way things are done every other day can be useful.
It is always a good idea to have some kind of an outlet (something to look forward to in the day whether it is lunch with a colleague, reading something of interest to you during a break, slight exercise walking if that is possible and maybe listening to hypnotic inductions during free time (there are many CDs out there to chose from) If you can listen to relaxing CDs there are also some that offer subliminally embedded messages (you would look for those about motivation, energy producing)
I was wondering if you may have adult ADD (although this is evident in childhood and adolescence and does not manifest in adulthood out of the blue) You may want to think if anything like this had occurred earlier in life (of if these behaviors only manifest when it comes to work related tasks) If you feel that it had occurred before, you could consult with a psychiatrist and there is ADD medication that is effective in managing the symptoms.