In this particular sentence, I believe the verb can only be in the plural. According to my favorite Grevisse (*Le français correct*, 1984):  

> (985) Subjects linked by AINSI QUE, COMME, AVEC, etc.  
> 
> a) If the conjunction is copulative ( = aggregates subject elements),
> the verb agrees with the whole:   Le français ainsi que l'italien
> DÉRIVENT du latin (Littré). - Aussi bien l'oncle Mathieu que tante
> Philomène n'ÉTAIENT pour moi que sons (H. Bosco). - La voix non plus
> que la silhouette ne lui ÉTAIENT connues (A. de Châteaubriant). - Le
> murmure des sources avec le hennissement des licornes se MÊLENT à
> leurs voix (Flaubert). - L'une comme l'autre GARDENT peu de loisir
> disponible pour l'aventure (M. Prévost). - Tant le sol boueux que
> l'eau m'ÉTAIENT présents (H. Bosco).  
> 
> b) If the conjunction clearly puts the elements in comparision, the
> agreement is with the first element:  
> Le français, ainsi que l'italien, DÉRIVE
> du latin (Littré). - Son visage, aussi bien que son cœur, AVAIT
> rajeuni de dix ans (Musset). - Le manque d'air ici, autant que
> l'ennui, FAIT bâiller (A. Gide). - L'un comme l'autre EST pris au jeu
> (Id.). - La religion, comme la politique, A ses Brutus (A. Hermant). -
> Renée, pas plus que Gilbert, n'ÉTAIT retournée chez les Guillaume (M.
> Arland).   
>
> Same (with AVEC), if one element is clearly accessory to the other:  
> Le travail
> avec ses servitudes lui INSPIRA de bonne heure un grand dégoût (M.
> Garçon).

In the present case, the mix of similitudes & divergences neither approaches nor opposes the desire to master the language; they are just two juxtaposed, separate incentives. The conjunction is copulative in meaning, not comparative, whence:  
  
... **m'ont** toujours motivé. 

(Edited after jlliagre's comments)

**Disclaimer.** My approach is *descriptive* not *prescriptive*, maybe I should add this to my SE profile. I am not a party in any effort at normalizing French, only explaining how I write it.  
In particular, I write w/o regard to the ongoing normalization process. I *guess* it systematically moves towards relaxing the rules I follow, not toward invalidating them; I have not checked though. **End of disclaimer.** 

Back to the question at hand: on the prescriptive side and as far as I know (which need not include the latest news, see above), school teachers are now instructed to accept both singular and plural in every instance, as reflecting the 2 equally valid intents of the writer.  

Finally, I will add a word about commas. Grevisse's examples clearly show they are optional and somehow related to the chosen agreement: his editors, if noone else, prefer them with the singular. However, he has not a word about them in the entire section I quoted, so I believe the subject is quite distinct.  
My own opinion is, punctuation comes *after* deciding the contents of the text and the comma basically marks where *speakers* pause; if they help silent *readers* (which they certainly do, so typesetters and editors will inevitably have their say about this), it is secondary.