I often tell fellow artists at demonstrations or workshops that it’s far better to draw and paint from your own sketches. Copying from a photograph can often be disappointing, as we all generally try to copy the photograph as carefully as we can. Often you will compare your picture against the photograph and be disappointed. So, you will improve your technique and style far quicker by working from your own sketches. Having nothing to compare it against, you will find your confidence and style will improve.
As always, there are exceptions to the rule.