[Grammar] Preposition, on; to; or with?

[Rollercoaster1]

Prepositions, are sometimes, one of the confusing problems among non-native English speakers, or learners.
I get confused sometimes as well.

A guy learns things, eg; computer prgramming, web designing, (sports) skiing, footballing, cricketing; but he doesn't masters/perfects/completes any of the things he does. He learns a bit and then leaves before completing any computer education, or sports.

If someone asks him about the completion of what he learns, and he responds "I couldn't achieve/complete (profession/study), because I am not/wasn't constant (on?to?with?) that. Which preposition is correct?

I prefer "on", but I need seniors' confirmation/answer.
Joe you know? I wasn't constant on learning things which I used to learn if I had learned, I would have been a multiskilled person.

 

[bhaisahab]

Your examples are not natural so it's not possible to answer your question in a meaningful way. You might say, "I didn't stick with the studies..."; "I didn't finish any of the courses...".

 

[Tdol]

Constant doesn't work for me either- you could use persist with.