1. your shaving skills might be lacking
2. the razor might not be shave ready (anymore)

Those are two big factors.

Number 1 you can work on, number 2 as well, but if you're not a little experienced as a razor honer that's probably gonna take some time as well.

As previously stated, pressure of the lack thereof is a huge deal. Also skin stretching, razor angle and a light touch go a long way.