Little warning:
Arguably, this contains scenes of 'forcing' (kisses) without John's verbal consent beforehand. However, John's okay with this, there was no sinister intent :)

John was an adrenaline addict, always craving a rush and powered by spontaneous events. One could argue that this was a reason for joining the army; the need for satisfaction caused by a constant addiction to dangerous, threatening and exciting situations. Or was this an effect of experiencing the battlefield, constant danger surrounding him and leaving him unable to cope without his fix of adrenaline? After the day he surprised Sherlock by essentially instructing him to kiss him, the detective wondered if an unplanned, spontaneous event between the two of them would cause John to react with higher levels of excitement and intensity. Perhaps, from time to time, he preferred spontaneity...

In order to test these effects, he decided to perform an experiment: to kiss his boyfriend without any warning or earlier discussion. He could then record the findings (tucking them safely away in his mind palace) and keep them safe, potentially for later use when the time was right...

He moved from the kitchen to the living room, eyes fixed on the tuft of dirty blond hair visible from behind the red chair. He removed the remote control from his grip, muting the blaring voices,  and lifted him to his feet by the hand, watching as his eyes displayed confusion and a question was quickly being formed in his mind. Before he could utter a word, Sherlock took his head in his large hands and shuffled one around to the back of his head, pressing their lips together softly. Upon impact, the kiss became much more advanced and Sherlock managed to enter John's mouth, snaking his tongue around the smaller man's and receiving soft moans as a result. His grip was firm, refusing to break the kiss at all. He attacked John's bottom lip, gently tugging and nipping at the centre.

Without warning, Johns knees gave way, causing him to sink into Sherlock's arms. The detective instantly panicked, detaching himself and staring worriedly into Johns eyes. His arms wrapped protectively around the man's sides and hauled his limp frame back up, holding on tight.

"Are you alright? Are you alright?"

"Sherlock, I'm fine." He chuckled, lips swollen and eyes sparkling.

"Have I done wrong?" Sherlock worried, already getting ready to apologise for his sudden outburst. John gazed up at him for a moment, the corners of his mouth pulling upwards to form a smile.

"No, you haven't." He rolled his eyes. "Come here."

He pulled Sherlock back down to his level, connecting them both once more. This kiss was much slower and lasted longer, elation filling the both of them. John's tender hands moved from around his lover's neck to around his sides, with Sherlock's around the doctor's waist.

This was definitely a successful experiment...