「Efforts to self-fellate by a fool」describes increasing EXASPERATED frustration and GROWING VIOLENT due to repeated failure in the attempt, finally SOLICITING HELP from those nearby, friends, family members, or a sympathetic bonobo. TO EXACERBATE a situation by demonstrating and then RECRUITING and CANVASSING candidates who only become jealous and INCREASINGLY VIOLENT as time goes on. Seeking money for charities and canvassing recruits to work or battle for the lord are subtly ridiculed as「efforts to self-fellate」a reference to both the high rate of disappointing failures and the extreme prideful joy experienced by an occasional success, feeling self-satisfied after locating another sucker, and with exceptional talent for that matter.
「Must never happen, foolish」or a literal「sunset」with「effort or power」together meaning either「never use your strength」in this manner, and「fool's strength」as references to the wasted spent effort of VIOLENCE. Perhaps a directive to「never use your strength by enlisting in the military」and「only a fool would use his strength by enlisting」(a reference only to ancient Chinese feudal military organizations of doubtful capability, and not to any modern institutions in which there is understandably great pride in the prowess to annihilate enemies). The idea of ENLISTMENT or RECRUITING at sunset stems from offering continued service in your own forces to defeated or captured enemies at the end of the battle day or politely suggesting they become ENLISTED as slaves, rather than beheading them, a thought that might be met with some of the enemy BECOMING INTENSE and EXACERBATING VIOLENCE as a result of either decision, or the mere suggestion even.「At sunset there is strength」perhaps is a reference to the INTENSE VIOLENCE at the end of a battle caused by beheading and then raping the defeated or captured forces, or vice-versa, rather than taking them as unhappy and rebellion-prone slaves or prisoners.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: canvass for contributions; to recruit; to collect; to raise
Japanese EDRDG: recruit, campaign, gather (contributions), enlist, grow violent
Unihan extended: levy, raise; summon; recruit