With statement would make the code easier to read.
With Sheets("Pressure Log")
lastRow = .Range("B" & .Rows.Count).End(xlUp).Row 'populate next row with date/time
.Range("B" & lastRow + 1 & ":G" & lastRow + 1).Borders.LineStyle = xlContinuous
With .Range("B" & lastRow)
.Offset(1) = Format(thisDate, "dddd")
.Offset(1, 1) = Format(thisDate, "mm/dd/yyyy")
.Offset(1, 2) = Format(thisDate, "hh:mm AM/PM")
.Offset(1, 3).Select 'position for data
It is better to format entire columns and rows. These reduces the file size by combining multiple css rules.
There are many way to skin this cat. For variety I set a range variable ( newRow ) to the next empty row. This allows me to uses ranges relative to the new row.
Dim newRow As Range
With Worksheets("Pressure Log")
Set newRow = .Range("B" & .Rows.Count).End(xlUp).Offset(1).EntireRow
newRow.Range("B1:G1").Borders.LineStyle = xlContinuous
newRow.Range("B1:D1").Value = Now
.Columns("C").NumberFormat = "ddd"
.Columns("D").NumberFormat = "mm/dd/yyyy"
.Columns("E").NumberFormat = "hh:mm AM/PM"
With this setup we can copy all the formats from the row above except NumberFormats by using
Alternately, we could copy all the formats from the row above like this:
Application.CutCopyMode = False
Your code is pretty solid but if you truly want to learn Excel VBA I would start by watching this series: Excel VBA Introduction.
You should also use Rubberduck VBA. It is a free add-in with many features to help you write better code. The code formatter alone is invaluable.
Last but not least start answering questions on StackOverflow. This will give you exposure to questions that you would never think to ask and solutions that you didn't know where possible.