I know what you mean!!! On Monday I took my Ruger Mark II apart and installed a plate to keep the mainspring pin from dropping under the cross pin. I have had this Mark II since 1984 and have had it apart probably 50 times and only had problems a couple of times. I went to reassembly the gun but couldn't get the mainspring back into the recess, I tried for about 3 hours on Monday, 2.5 hours on Tuesday and .30 minutes on Wednesday, all went together fine and easy peasy. Sometimes is pays to just walk away frustrated can come back to it later which works most of the time.