My mum is going into hospital on Wednesday for an operation: of your charity, please keep her in your prayers.
Matthias (see comments) suggested Psalm 27 (26 in the Vulgate) as a good prayer to pray; here it is in the Grail Version familiar to me from the modern Divine Office:
Psalm 27(26) Dominus illuminatio
1 The Lord is my light and my help;
whom shall I fear?
The Lord is the stronghold of my life;
before whom shall I shrink?
2 When evil-doers draw near
to devour my flesh,
it is they, my enemies and foes,
who stumble and fall.
3 Though an army encamp against me
my heart would not fear.
Though war break out against me
even then would I trust.
4 There is one thing I ask of the Lord,
for this I long,
to live in the house of the Lord,
all the days of my life,
to savor the sweetness of the Lord,
to behold his temple.
5 For there he keeps me safe in his tent
in the day of evil.
He hides me in the shelter of his tent,
on a rock he sets me safe.
6 And now my head shall be raised
above my foes who surround me
and I shall offer within his tent
a sacrifice of joy.
I will sing and make music for the Lord.
7 O Lord, hear my voice when I call;
have mercy and answer.
8 Of you my heart has spoken:
"Seek his face."
It is your face, O Lord, that I seek;
9 hide not your face.
Dismiss not your servant in anger;
you have been my help.
Do not abandon or forsake me,
O God my help!
10 Though father and mother forsake me,
the Lord will receive me.
11 Instruct me, Lord, in your way;
on an even path lead me.
12 When they lie in ambush protect me
from my enemy's greed.
False witnesses rise against me,
breathing out fury.
13 I am sure I shall see the Lord's goodness
in the land of the living.
14 Hope in him, hold firm and take heart.
Hope in the Lord!