Beechcraft Bonanza pilot reported descending toward terrain while attempting to remain VFR below lowering cloud deck. Pilot climbed into clouds and after re-entering VFR conditions diverted to a suitable airport.

Narrative

Flight from ZZZ1 to ZZZ. ZZZ forecast was marginal VFR with improving conditions. Conditions 30-60 miles south of the airport were much better and the weather was moving north so I anticipated improvement. Easy to stay VFR for 80 percent of the flight. Between broken layers at worst. Had to stay east of direct track to avoid moderate to heavy rain and low ceilings. Twenty-five minutes or so from destination; I descended below broken layer while easily maintaining visibility and cloud clearance requirements. Ceiling continued to lower and I descended to stay below it. At time of incident; believe I was east-northeast of ZZZ (reporting 1100 broken I believe at the time). I was at 2000 MSL (unsure of AGL as I was over the hills/valleys). Flight is getting uncomfortable now given need to stay out of clouds and still comply with minimum safe altitudes. Ceiling continued to lower and I thought I set altitude alerter for 1800 MSL and started a 300 fpm decent. Looked down at the chart to confirm terrain/Tower clearance ahead and to attempt to stay out of any lower class E airspace. Out of the corner of my eye; I saw the ground rushing past indicating the aircraft was at an altitude I felt was too low. At the same time I entered clouds and lost visibility briefly (felt like 5 seconds). Looked at altimeter and saw I was approaching 1700 ft. (altitude had not captured). The proximity to the ground was not comfortable and I knew the layer above me was thin so even though I could see again; I pulled up into the clouds. Broke out around 2500 ft. MSL and proceeded to ZZZ2 where I could land VFR.As for lessons learned...ha!...many. I'm employed as a commercial pilot and have not scared myself in many years. Not sure if it was arrogance or overconfidence or what; but I badly underestimated the difficulty of completing this flight. This was one of those situations where I got on the ground and felt stupid and unprofessional. I relearned lessons about scud running and just how difficult and busy it can get trying to look ahead at what's coming; maintain cloud clearance and ground clearance; and manage flying the airplane. I must have mismanaged the Autopilot given the decent below my selected altitude of 1800. The Bonanza is a relatively fast aircraft and the ground moves by quickly. Flying VFR in 'marginal VFR' conditions is technically legal; but it may not be smart. Never again.