Okay, I might be very wide of the mark. The Doctor is depressed, but he always travels with someone he loves, namely the Tardis, and maybe this is one way the Tradis thinks it is helping the Doctor. The Tardis exists in all time and space, knows what interests the Doctor and what makes him tick. Now with Clara, it's got the Doctor back. Must have learnt a lot since the Doctor's Wife and is being a lot sneakier. Healing the Doctor without him knowing. Might explain the kissing as well.