One of the posters mentioned new equipment and it reminded me of something I would appreciate being confirmed or disputed.
I have been told (and it makes sense to me) that a new wetsuit shows a lot more variance in buoyancy over the first 20 or so dives than it wil later in life, meaning that as you break in a new suit you need to keep an eye on you weighting as a brand new suit may require more weight than an older suit to sink it ( hence the difference with battered rental suits).
On another point.
When I did my OW the instructor would make us descend to the bottom, gather us together and do skills, ending in fin pivot/hover before we swam off, and similar happened on checkout dives. It wasn't until my first proper (nontraining) dives that I realised that I should be neutral before reaching the bottom. Once I mastered dropping horizontally into a graceful stop in a hover a meter above the bottom I felt great about my diving, similarly when I mastered setting myself down on the bottom and 'lifting' off again using just my lungs.
These are actually the moments that make me feel like I might be a diver rather than someone who can swim under water with SCUBA