Yes, it is a matter of the heart, that is very true . . . however:
Jer 17:9 The heart is deceitful above all things, and desperately wicked: who can know it?
Joy is an issue of the heart . . the belief Jesus ascribes to those who are the rocky soil is much more than a mental belief . . it is a belief of the heart, for it is accompanied by joy - Again:
Luk 8:13 They on the rock are they, which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away.
"receive"
G1209
δέχομαι
dechomai
Thayer Definition:
1) to take with the hand
1a) to take hold of, take up
2) to take up, receive
2a) used of a place receiving one
2b) to receive or grant access to, a visitor, not to refuse intercourse or friendship
2b1) to receive hospitality
2b2) to receive into ones family to bring up or educate
2c) of the thing offered in speaking, teaching, instructing
2c1) to receive favourably, give ear to, embrace, make ones own, approve, not to reject2d) to receive. i.e. to take upon ones self, sustain, bear, endure
3) to receive, get
3a) to learn
Part of Speech: verb
A Related Word by Thayers/Strongs Number: middle voice of a primary verb
Citing in TDNT: 2:50, 146
So there is full acceptance of the thing taught . . Here, the Gospel of Christ . . .
"joy"
G5479
χαρά
chara
khar-ah'
From G5463; cheerfulness, that is, calm delight: - gladness, X greatly, (X be exceeding) joy (-ful, -fully, -fulness, -ous).
So, this is teaching that has been embraced, accepted fully, made one's own with exceeding joy . . .
"believe"
G4100
πιστεύω
pisteuō
pist-yoo'-o
From G4102; to have faith (in, upon, or with respect to, a person or thing), that is, credit; by implication to entrust (especially ones spiritual well being to Christ): - believe (-r), commit (to trust), put in trust with.
G4100
πιστεύω
pisteuō
Thayer Definition:
1) to think to be true, to be persuaded of, to credit, place confidence in
1a) of the thing believed
1a1) to credit, have confidence
1b) in a moral or religious reference
1b1) used in the NT of the conviction and trust to which a man is impelled by a certain inner and higher prerogative and law of soul
1b2) to trust in Jesus or God as able to aid either in obtaining or in doing something: saving faith
2) to entrust a thing to one, i.e. his fidelity
2a) to be intrusted with a thing
Part of Speech: verb
A Related Word by Thayers/Strongs Number: from G4102
Citing in TDNT: 6:174, 849
This is true, real belief . . real trust in Christ . .
saving faith!
Jesus is speaking of
REAL belief . . not a false belief . .
And yet, because the ground was not good enough to allow this faith to persevere, the person will not endure in a time of temptation and will
fall away . . . .
This is demonstrating the process of salvation . . we currently have the hope of our salvation. Final salvation is not ours until we leave this world in a state of divine sanctifying grace . . in friendship with God.
And so we must do something . . . we must tend our garden . . . .we must till it, keep it free from weeds and insects . . .
So yes, we must do something . . . .
.